2. To strike or beat with something hard or heavy; to rap; as, to knock with a club; to knock on the door. [ 1913 Webster ]

For harbor at a thousand doors they knocked. Dryden. [ 1913 Webster ]

Seek, and ye shall find; knock, and it shall be opened unto you. Matt. vii. 7. [ 1913 Webster ]

3. To practice evil speaking or fault-finding; to criticize habitually or captiously. [ Slang, U. S. ] [ Webster 1913 Suppl. ]

To knock about, to go about, taking knocks or rough usage; to wander about; to saunter. [ Colloq. ] “Knocking about town.” W. Irving. --
To knock up, to fail of strength; to become wearied or worn out, as with labor; to give out. “The horses were beginning to knock up under the fatigue of such severe service.” De Quincey. --
To knock off, to cease, as from work; to desist. --
To knock under, to yield; to submit; to acknowledge one's self conquered; -- an expression probably borrowed from the practice of knocking under the table with the knuckles, when conquered. “Colonel Esmond knocked under to his fate.” Thackeray. [ 1913 Webster ]

When heroes knock their knotty heads together. Rowe. [ 1913 Webster ]

2. To strike for admittance; to rap upon, as a door. [ 1913 Webster ]

Master, knock the door hard. Shak. [ 1913 Webster ]

3. To impress strongly or forcibly; to astonish; to move to admiration or applause. [ Slang, Eng. ] [ Webster 1913 Suppl. ]

4. To criticise; to find fault with; to disparage. “Don't knock it if you haven't tried it.” [ PJC ]

To knock in the head, or
To knock on the head, to stun or kill by a blow upon the head; hence, to put am end to; to defeat, as a scheme or project; to frustrate; to quash. [ Colloq. ] --
To knock off. (a) To force off by a blow or by beating. (b) To assign to a bidder at an auction, by a blow on the counter. (c) To leave off (work, etc.). [ Colloq. ] --
To knock out, to force out by a blow or by blows; as, to knock out the brains. --
To knock up. (a) To arouse by knocking. (b) To beat or tire out; to fatigue till unable to do more; as, the men were entirely knocked up. [ Colloq. ] “The day being exceedingly hot, the want of food had knocked up my followers.” Petherick. (c) (Bookbinding) To make even at the edges, or to shape into book form, as printed sheets. (d) To make pregnant. Often used in passive, "she got knocked up". [ vulgar ]

2. A stroke, as on a door for admittance; a rap. “ A knock at the door.” Longfellow. [ 1913 Webster ]

A loud cry or some great knock. Holland. [ 1913 Webster ]

Knock off, See knock off in the vocabulary. [ PJC ]

2. A knockabout performer or performance. [ Theat. Slang ] [ Webster 1913 Suppl. ]

3. A man hired on a sheep station to do odd jobs. [ Colloq., Australia ] [ Webster 1913 Suppl. ]

2. Of noisy and violent character; marked by farce, pratfalls, and horseplay; as, knockabout comedy. [ Theat. Slang ]
Syn. -- boisterous, slapstick. [ Webster 1913 Suppl. ]

3. Characterized by, or suitable for, knocking about, or traveling or wandering hither and thither; suitable for use in rough activity; suited for everyday use; -- used especially of clothing.
Syn. -- casual, everyday. [ Webster 1913 Suppl. ]

4. That does odd jobs; -- said of a class of hands or laborers on a sheep station. [ Collog., Australia ] [ Webster 1913 Suppl. ]

2. A knocking down; a felling by a knock, as of a combatant, or of an animal; a blow that overwhelms; also, a fist fight. [ Webster 1913 Suppl. ]

3. Something that knocks down, or takes apart, for packing or removal, as a piece of furniture; also, state of being knocked down, or taken apart. [ Webster 1913 Suppl. ]

2. Designating a rivet end to be formed into a head by upsetting in fastening. [ Webster 1913 Suppl. ]

3. Of or pertaining to the act of knocking down at an auction; specif., designating the price below which an article will not be disposed by the auctioneer. [ Webster 1913 Suppl. ]

4. Made or constructed so as to be capable of being knocked down or taken apart, as for transportation. [ Webster 1913 Suppl. ]

2. To assign to a bidder at an auction, by a blow or knock of the auctioneer's hammer; to sell at an auction; as, the vase was knocked down at two thousand dollars. [ 1913 Webster +PJC ]

3. To take apart; to dissassemble; as, to knock down a rifle for cleaning. [ PJC ]

4. To reduce or discount the price of; as, the dresses were knocked down to twenty dollars. [ PJC ]

5. To earn (an income). “plumbers who knock down over a hundred thousand a year.” [ PJC ]