Source : Webster's Revised Unabridged Dictionary (1913)

Offshore \Off"shore"\, a.
   From the shore; as, an offshore wind; an offshore signal.

Source : WordNet®

offshore
     adj 1: (of winds) coming from the land; "offshore winds" [ant: {inshore}]
     2: at some distance from the shore; "offshore oil reserves";
        "an offshore island"
     adv : away from shore; away from land; "cruising three miles
           offshore" [ant: {onshore}]