The Collaborative International Dictionary of English v.0.48:
Knock \Knock\ (n[o^]k), v. i. [imp. & p. p. Knocked (n[o^]kt);
p. pr. & vb. n. Knocking.] [OE. knoken, AS. cnocian,
cnucian; prob. of imitative origin; cf. Sw. knacka. Cf.
1. To drive or be driven against something; to strike against
something; to clash; as, one heavy body knocks against
2. To strike or beat with something hard or heavy; to rap;
as, to knock with a club; to knock on the door.
For harbor at a thousand doors they knocked.
Seek, and ye shall find; knock, and it shall be
opened unto you. --Matt. vii.
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.