The Collaborative International Dictionary of English v.0.48:

Yaw \Yaw\, n. (Naut.)
   A movement of a vessel by which she temporarily alters her
   course; a deviation from a straight course in steering.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Yaw \Yaw\ (y[add]), v. i. [imp. & p. p. Yawed (y[add]d); p.
   pr. & vb. n. Yawing.] [Cf. Yew, v. i.]
   To rise in blisters, breaking in white froth, as cane juice
   in the clarifiers in sugar works.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Yaw \Yaw\, v. i. & t. [Cf. Prov. G. gagen to rock, gageln to
   totter, shake, Norw. gaga to bend backward, Icel. gagr bent
   back, gaga to throw the neck back.] (Naut.)
   To steer wild, or out of the line of her course; to deviate
   from her course, as when struck by a heavy sea; -- said of a
   ship.
   [1913 Webster]

         Just as he would lay the ship's course, all yawing
         being out of the question.               --Lowell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

yaw
    n 1: an erratic deflection from an intended course [syn: yaw,
         swerve]
    v 1: be wide open; "the deep gaping canyon" [syn: gape,
         yawn, yaw]
    2: deviate erratically from a set course; "the yawing motion of
       the ship"
    3: swerve off course momentarily; "the ship yawed when the huge
       waves hit it"