The Collaborative International Dictionary of English v.0.48:

overhanded \overhanded\ adj.
   performed with the arm moving above the shoulder;
   overhand[2]; -- of methods of throwing, especially in
   baseball. Contrasted with underhand and sidearm.

   Syn: overarm.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

overhanded
    adj 1: with hand brought forward and down from above shoulder
           level; "an overhand pitch"; "an overhand stroke" [syn:
           overhand, overhanded, overarm] [ant: underarm,
           underhand, underhanded]