Holy

You are to distinguish between the holy and the common, and between the unclean and the clean, and you are to teach the people of Israel all the statutes that the LORD has spoken to them by Moses. -- Leviticus 10:10-11 (ESV)

Secular definition of Holy

Strong's Concordance define "holy" in Hebrew as:

qadosh            : sacred, holy
Original Word     : קָדוֹשׁ
Part of Speech    : Adjective
Transliteration   : qadosh
Phonetic Spelling : (kaw-doshe')
Definition        : sacred, holy

Or in Greek:

hagios            : sacred, holy
Original Word     : ἅγιος, ία, ον
Part of Speech    : Adjective
Transliteration   : hagios
Phonetic Spelling : (hag'-ee-os)
Definition        : sacred, holy

So, according to Strong's Concordance "holy" means "sacred". It is surprisingly hard to find a proper definition of "holy" or "sacred" in English dictionaries which seems to contradict each other. However, commonly most agree that "sacred" means:

  1. made, declared, or believed to be holy; devoted to a deity or some religious ceremony or use
  2. worthy of religious veneration
  3. concerned with religion or religious purposes
  4. worthy of respect or dedication
  5. (often followed by `to') devoted exclusively to a single use or purpose or person

-- vocabulary.com

Biblical definition of Holy

YHVH is holy, which means He is:

Any persons or item that is holy means that the person, or it has to:

In addition, the following is also considered holy:

Holiness of God

Are You not from everlasting, O LORD my God, my Holy One?

We shall not die.

  • O LORD, You have appointed them for judgment;
  • O Rock, You have marked them for correction.
  • You are of purer eyes than to behold evil, and cannot look on wickedness.

-- Habakkuk 1:12 (NKJV)

In other words, according to Habakkuk, the "Holy One" is:

Just Judge

I will not execute my burning anger; I will not again destroy Ephraim; for I am God and not a man, the Holy One in your midst, and I will not come in wrath. -- Hosea 11:9 (ESV)

Almighty God

Then He (YHVH) struck the men of Beth Shemesh, because they had looked into the ark of the LORD. He struck fifty thousand and seventy men of the people, and the people lamented because the LORD had struck the people with a great slaughter.

And the men of Beth Shemesh said,

“Who is able to stand before this holy LORD God?
And to whom shall it go up from us?”

-- 1 Samuel 6:19-20 (NKJV)

Worthy of dedication

The four living creatures, each having six wings, were full of eyes around and within. And they do not rest day or night, saying:

“Holy, holy, holy, Lord God Almighty, Who was and is and is to come!”

Whenever the living creatures give glory and honor and thanks to Him who sits on the throne, Who lives forever and ever, the twenty-four elders fall down before Him who sits on the throne and worship Him who lives forever and ever, and cast their crowns before the throne, saying:

“You are worthy, O Lord, to receive glory and honor and power; For You created all things, and by Your will they exist and were created.”

-- Revelation 4:8-11 (NKJV)

Pure and clean

For I am the LORD your God.

  • Consecrate yourselves (set yourself apart) therefore, and be holy, for I am holy.
  • You shall not defile yourselves with any swarming thing that crawls on the ground.

For I am the LORD who brought you up out of the land of Egypt to be your God. You shall therefore be holy, for I am holy.”

-- Leviticus 11:44-45 (ESV)

God will not defile Himself. Therefore, if you want to serve God, you had to be clean.

But Joshua said to the people, “You are not able to serve the LORD, for He is a holy God. He is a jealous God; he will not forgive your transgressions or your sins. -- Joshua 24:19 (ESV)

Therefore, everything dedicated to God is also considered Holy to avoid contamination of uncleanness.

Holiness of creation

Created persons or items is considered holy when they are set apart exclusively for YHVH's purpose or ownership. Since YHVH Himself is pure and clean, anything in His presence should also be pure, clean and righteous. Therefore, the priests had to do proper sacrificial worship and cleaning before they were allowed to enter the most holy place of God. Likewise, no human has access to YHVH without the sacrificial blood of Jesus Christ our mediator to God who washes believers clean from sin so that they too may be holy.

Clean

“Thus says the LORD of hosts:

Ask the priests about the law: ‘If someone carries holy meat in the fold of his garment and touches with his fold bread or stew or wine or oil or any kind of food, does it become holy?’”
The priests answered and said, “No.”
Then Haggai said, “If someone who is unclean by contact with a dead body touches any of these, does it become unclean?”
The priests answered and said, “It does become unclean.”

-- Haggai 2:11-13 (ESV)

If you want to be God's child in His presence, you should be holy too:

As obedient children, do not be conformed to the passions of your former ignorance, but as He who called you is holy, you also be holy in all your conduct, since it is written, “You shall be holy, for I am holy.” -- 1 Peter 1:14-16 (ESV)

This is why sin is such a big deal. It makes one "unclean" and causes separation between you and God.

Dedication

Hannah's dedication:

"For this child I prayed, and the Lord has granted me my petition which I asked of Him. Therefore I also have lent him to the LORD; as long as he lives he shall be lent to the LORD."

So they worshiped the LORD there.

And Hannah prayed and said:

“My heart rejoices in the Lord;
My horn is exalted in the Lord.
smile at my enemies,
Because I rejoice in Your salvation.
No one is holy like the LORD, for there is none besides You, nor is there any rock like our God."

-- 1 Samuel 1:24-2:2 (NKJV)

Other things that are considered Holy which God had considered holy:

God's angel:

  • Holy One referred as a "watcher" (Daniel 4:13, 23; 8:13)

God's time:

  • Holy Sabbath (Genesis 2:3; Exodus 16:22-26, 31:14-15, 35:2; Deuteronomy 5:12)

God's people:

  • God's Son (Luke 1:35; Acts 2:27 & 13:35 quoting Psalm 16:10; Hebrews 7:26)
  • Holy Children (1 Peter 1:14-16)
  • Holy Assembly (Exodus 12:16-17)
  • Holy Nation (Exodus 19:3-6; Leviticus 19:1-2, 20:7)
  • Holy Priests (Exodus 29:21, 29:32-33, 30:29-30; Leviticus 21:1-9; Hebrews 7:26)
  • Holy Prophets (2 Peter 3:1-2)

God's places:

  • Holy Place (Exodus 3:4-5, 15:13, 26:33-34, 28:35, 28:42-43, 29:31, 40:9-11, Joshua 5:15)
  • Holy Temple (Psalm 5:7, 11:4, 138:2; 1 Kings 7:48-50; Habakkuk 2:20; Jonah 2:4)
  • Holy Mountain (Joel 2:1, 3:17; Obadiah 1:16)
  • Holy Land (Zechariah 2:12)
  • Holy City (Joel 3:17; Revelation 21:10-11)

God's objects:

  • Holy Bread (Leviticus 21:6)
  • Holy Garments (Exodus 28:2-4, 29:21,29)
  • Holy Offerings (Exodus 28:38; Leviticus 2:3,10, 6:25-30, 19:23-24, 27:14, 27:21-23, 27:28-30; Numbers 5:9-10)
  • Holy Crown (Exodus 28:36, 29:6, 39:30)
  • Holy Anointing Oil (Exodus 30:33)
  • Holy Incense (Exodus 30:34-38)
  • Holy Altar (Exodus 40:10)
  • Holy Water (Numbers 5:17)
  • Holy Treasures (Joshua 6:19)
  • Holy Ark (2 Chronicles 35:3)