|Easton's Bible Dictionary|
"Though Orientals are very jealous of their privacy, they never knock when about to enter your room, but walk in without warning or ceremony. It is nearly impossible to teach an Arab servant to knock at your door. They give warning at the outer gate either by calling or knocking. To stand and call is a very common and respectful mode. Thus Moses commanded the holder of a pledge to stand without and call to the owner to come forth (Deuteronomy 24:10). This was to avoid the violent intrusion of cruel creditors. Peter stood knocking at the outer door (Acts 12:13, 16), and the three men sent to Joppa by Cornelius made inquiry and `stood before the gate' (10:17, 18). The idea is that the guard over your privacy is to be placed at the entrance."
Knocking is used as a sign of importunity (Matthew 7:7, 8; Luke 13:25), and of the coming of Christ (Luke 12:36; Revelation 3:20).
Noah Webster's Dictionary
1. (v. i.) To drive or be driven against something; to strike against something; to clash; as, one heavy body knocks against another.
2. (v. i.) To strike or beat with something hard or heavy; to rap; as, to knock with a club; to knock on the door.
3. (v. t.) To strike with something hard or heavy; to move by striking; to drive (a thing) against something; as, to knock a ball with a bat; to knock the head against a post; to knock a lamp off the table.
4. (v. t.) To strike for admittance; to rap upon, as a door.
5. (n.) A blow; a stroke with something hard or heavy; a jar.
6. (n.) A stroke, as on a door for admittance; a rap.
Int. Standard Bible Encyclopedia
nok (krouo): The oriental house was fitted with heavy doors which were bolted and locked with wooden keys too large to be carried about, so that even a member of the household could not secure entrance until in response to his knock or call the door should be opened by someone within. At night the delay would be increased by the difficulty of arousing the inmates sleeping within the inner chambers. To persons familiar with such experiences, the words of Jesus concerning a higher entrance, "Knock, and it shall be opened unto you" (Matthew 7:7 Luke 12:36), would have a unique force not easy for us to appreciate.
Russell Benjamin Miller
Knock (7 Occurrences)
Matthew 7:7 "Ask, and it will be given you. Seek, and you will find. Knock, and it will be opened for you. (WEB KJV WEY ASV DBY WBS YLT NAS RSV NIV)
Luke 11:9 "I tell you, keep asking, and it will be given you. Keep seeking, and you will find. Keep knocking, and it will be opened to you. (Root in WEB KJV WEY ASV DBY WBS YLT NAS RSV NIV)
Luke 13:25 When once the master of the house has risen up, and has shut the door, and you begin to stand outside, and to knock at the door, saying,'Lord, Lord, open to us!' then he will answer and tell you,'I don't know you or where you come from.' (WEB KJV WEY ASV DBY WBS YLT NAS RSV NIV)
Acts 12:13 When Peter knocked at the door of the gate, a maid named Rhoda came to answer. (Root in WEB KJV WEY ASV DBY WBS YLT NAS RSV NIV)
Revelation 3:20 Behold, I stand at the door and knock. If anyone hears my voice and opens the door, then I will come in to him, and will dine with him, and he with me. (WEB KJV WEY ASV DBY WBS YLT NAS RSV NIV)
Exodus 21:27 And if he knock out his bondman's tooth or his handmaid's tooth, he shall let him go free for his tooth. (DBY YLT NAS RSV NIV)
Nahum 2:10 She is empty, void, and waste. The heart melts, the knees knock together, their bodies and faces have grown pale. (WEB NAS)