to knock on the head

Knock \Knock\ (n[o^]k), v. t.
   1. 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.
      [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]