Source : Webster's Revised Unabridged Dictionary (1913)

Leeway \Lee"way`\ (l[=e]"w[=a]`), n. (Naut.)
   The lateral movement of a ship to the leeward of her course;
   drift.

Source : WordNet®

leeway
     n 1: (of a ship or plane) sideways drift
     2: a permissible difference; allowing some freedom to move
        within limits [syn: {allowance}, {margin}, {tolerance}]