The Collaborative International Dictionary of English v.0.48:
Leeway \Lee"way`\ (l[=e]"w[=a]`), n. (Naut.) The lateral movement of a ship to the leeward of her course; drift. [1913 Webster]WordNet (r) 3.0 (2006):
leeway n 1: (of a ship or plane) sideways drift 2: a permissible difference; allowing some freedom to move within limits [syn: allowance, leeway, margin, tolerance]