Knock v. i. [imp. & p. p. Knocked p. pr. & vb. n. Knocking.]
 1. To drive or be driven against something; to strike against something; to clash; as, one heavy body knocks against another.
 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.   --Dryden.
    Seek, and ye shall find; knock, and it shall be opened unto you.   --Matt. vii. 7.
 3. To practice evil speaking or fault-finding; to criticize habitually or captiously. [Slang, U. S.]
 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.


 Knuc·kle, v. i. [imp. & p. p. Knuckled ; p. pr. & vb. n. Knuckling ] To yield; to submit; -- used with down, to, or under.
 To knuckle to. (a) To submit to in a contest; to yield to. [Colloq.] See To knock under, under Knock, v. i.  (b) To apply one's self vigorously or earnestly to; as, to knuckle to work. [Colloq.]