The Collaborative International Dictionary of English v.0.48:

Handicap \Hand"i*cap\, v. t. [imp. & p. p. Handicapped
   (-k[a^]pt); p. pr. & vb. n. Handicapping.]
   To encumber with a handicap in any contest; hence, in
   general, to place at disadvantage; as, the candidate was
   heavily handicapped.
   [1913 Webster]