The Collaborative International Dictionary of English v.0.48:

Landlubber \Land"lub`ber\, n. [Prop. fr. land + lubber, or
   possibly corrupted fr. laudlouper.] (Naut.)
   One who passes his life on land; -- so called among seamen in
   contempt or ridicule.
   [1913 Webster]

WordNet (r) 3.0 (2006):

landlubber
    n 1: a person who lives and works on land [syn: landlubber,
         landsman, landman]
    2: an inexperienced sailor; a sailor on the first voyage [syn:
       landlubber, lubber, landsman]