[syn: underarm, underhand]
The Collaborative International Dictionary of English v.0.48:
Underhand \Un"der*hand`\ ([u^]n"d[~e]r*h[a^]nd`), a.
   1. Secret; clandestine; hence, mean; unfair; fraudulent.
      --Addison.
      [1913 Webster]
   2. (Baseball, Cricket, etc.) Done, as pitching, with the hand
      lower than the shoulder, or, as bowling, with the hand
      lower than the elbow.
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Underhand \Un"der*hand`\ ([u^]n"d[~e]r*h[a^]nd`), adv.
   1. By secret means; in a clandestine manner; hence, by fraud;
      unfairly; dishonorably.
      [1913 Webster]
            Such mean revenge, committed underhand. --Dryden.
      [1913 Webster]
            Baillie Macwheeble provided Janet, underhand, with
            meal for their maintenance.           --Sir W.
                                                  Scott.
      [1913 Webster]
   Note: In modern usage, the sense is usually negative.
         [PJC]
   2. (Baseball, Cricket, etc.) In an underhand manner; thrown
      with the hand no higher than the shoulder and the palm
      turned upward during part of the pitch; -- said of
      pitching or bowling a ball.
      [1913 Webster +PJC]
WordNet (r) 3.0 (2006):
underhand
    adv 1: slyly and secretly; "Mean revenge, committed underhand"-
           John Donne; "oldline aristocratic diplomats underhandedly
           undermined the attempt...to align Germany with the
           Western democracies"- C.G.Bowers [syn: underhandedly,
           underhand]
    2: with the hand swung below shoulder level; "throwing a ball
       underarm" [syn: underarm, underhand]
    adj 1: with hand brought forward and up from below shoulder
           level; "an underhand pitch"; "an underhand stroke" [syn:
           underhand, underhanded, underarm] [ant: overarm,
           overhand, overhanded]
    2: marked by deception; "achieved success in business only by
       underhand methods" [syn: sneaky, underhand,
       underhanded]
Moby Thesaurus II by Grady Ward, 1.0:
20 Moby Thesaurus words for "underhand":
   crafty, crooked, cunning, deceitful, devious, dishonest,
   duplicitous, furtive, guileful, hangdog, indirect, insidious,
   oblique, shifty, sly, sneaking, sneaky, tricky, underhanded,
   wily