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]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "leeway":
   aesthetic distance, air space, ample scope, blank check, caesura,
   carte blanche, clearance, compass, deep space, depths of space,
   discontinuity, distance, distance between, divergence,
   double space, drift, driftway, elbowroom, em space, en space,
   extent, farness, field, free course, free hand, free play,
   free scope, freeboard, freedom, full scope, full swing, hair space,
   half space, headroom, headway, hiatus, infinity, interim,
   intermediate space, interruption, interspace, interstice, interval,
   jump, lacuna, latitude, leap, length, light-years, long rope,
   maneuvering space, margin, mileage, no holds barred, open space,
   parsecs, perspective, piece, play, progress, range, reach,
   remoteness, room, room to spare, rope, scope, sea room, separation,
   single space, slack, space, space between, span, spare room,
   steerageway, sternway, stretch, stride, swing, time interval,
   tolerance, way, ways, wide berth