The Collaborative International Dictionary of English v.0.48:

Nudge \Nudge\ (n[u^]j), v. t. [imp. & p. p. Nudged (n[u^]jd);
   p. pr. & vb. n. Nudging.] [Cf. Prov. G. kn["u]tschen to
   squeeze, pinch, E. Knock.]
   To touch gently, as with the elbow, in order to call
   attention or convey intimation.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nudge \Nudge\, n.
   A gentle push, or jog, as with the elbow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nudge
    n 1: a slight push or shake [syn: nudge, jog]
    v 1: to push against gently; "She nudged my elbow when she saw
         her friend enter the restaurant" [syn: nudge, poke at,
         prod]
    2: push into action by pestering or annoying gently