The Collaborative International Dictionary of English v.0.48:

Gyb \Gyb\ (j[i^]b), Gybe \Gybe\ (j[imac]b), n. (Naut.)
   See Jib. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gybe \Gybe\ (j[imac]b), n. & v.
   See Gibe.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gybe \Gybe\, v. t. & i. [imp. & p. p. Gybed (j[imac]bd); p.
   pr. & vb. n. Gybing.] [See Jibe.] (Naut.)
   To shift from one side of a vessel to the other; -- said of
   the boom of a fore-and-aft sail when the vessel is steered
   off the wind until the sail fills on the opposite side. [Also
   jibe.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

gybe
    v 1: shift from one side of the ship to the other; "The sail
         jibbed wildly" [syn: jibe, gybe, jib, change
         course]