The Collaborative International Dictionary of English v.0.48:

Frap \Frap\, v. t. [imp. & p. p. Frapped; p. pr. & vb. n.
   Frapping.] [Cf. F. frapper to strike, to seize ropes. Cf.
   Affrap.]
   1. (Naut.) To draw together; to bind with a view to secure
      and strengthen, as a vessel by passing cables around it;
      to tighten; as a tackle by drawing the lines together.
      --Tottem.
      [1913 Webster]

   2. To brace by drawing together, as the cords of a drum.
      --Knoght.
      [1913 Webster]

WordNet (r) 3.0 (2006):

frap
    v 1: make secure by lashing; "frap a sail"
    2: take up the slack of; "frap a rope"