1. Thin and weak
   "a wispy little fellow with small hands and feet";
   - wisplike
    
2. Lacking clarity or distinctness
   "a few wispy memories of childhood";
   - dim, faint, shadowy, vague

Derived forms: wispiest, wispier

See also: indistinct, lean, meager [N. Amer], meagre [Brit, Cdn], thin