The Collaborative International Dictionary of English v.0.48:

Nock \Nock\, n. [See Notch.]
   1. A notch.
      [1913 Webster]

            He took his arrow by the nock.        --Chapman.
      [1913 Webster]

   2. (Naut.) The upper fore corner of a boom sail or of a
      trysail.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nock \Nock\, v. t.
   To notch; to fit to the string, as an arrow; to string, as a
   bow. --Chapman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nock
    v 1: make small marks into the surface of; "score the clay
         before firing it" [syn: score, nock, mark]