What is "to knock in 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.

   When heroes knock their knotty heads together.
   --Rowe.

2. To strike for admittance; to rap upon, as a door.

   Master, knock the door hard.
   --Shak.

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

4. To criticise; to find fault with; to disparage. ``Don't knock it if you haven't tried it.'' 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.

   1. To force off by a blow or by beating.

   2. To assign to a bidder at an auction, by a blow on the counter.

   3. 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.

      1. To arouse by knocking.

      2. 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.

      3. (Bookbinding) To make even at the edges, or to shape into book form, as printed sheets.

   4. To make pregnant. Often used in passive, "she got knocked up". [vulgar]