WordWeb Online

1. Lacking grace in movement or posture
   "a gawky lad with long ungainly legs"; "what an ungainly creature a giraffe is"; "a clunky lad with long ungainly legs"; "a klutzy lad with long ungainly legs";
   - gawky, clumsy, clunky, unwieldy, klutzy [N. Amer]
    
2. Difficult to handle or manage especially because of shape
   "the cello, a rather ungainly instrument for a girl";
   - awkward, bunglesome, clumsy

Derived forms: ungainliest, ungainlier

See also: awkward, unmanageable, unwieldy