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.
   Knack.]
   1. To drive or be driven against something; to strike against
      something; to clash; as, one heavy body knocks against
      another. --Bacon.
      [1913 Webster]

   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]

The Collaborative International Dictionary of English v.0.48:

Knocking \Knock"ing\, n.
   A beating; a rap; a series of raps.
   [1913 Webster]

         The . . . repeated knockings of the head upon the
         ground by the Chinese worshiper.         --H. Spencer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

knocking
    n 1: the sound of knocking (as on a door or in an engine or
         bearing); "the knocking grew louder" [syn: knock,
         knocking]