WordNet (r) 3.0 (2006):

capital punishment
    n 1: putting a condemned person to death [syn: execution,
         executing, capital punishment, death penalty]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "capital punishment":
   beheading, burning, crucifixion, decapitation, decollation,
   defenestration, electrocution, execution, fusillade, garrote,
   gassing, hanging, hemlock, judicial murder, lapidation,
   necktie party, poisoning, shooting, stoning, strangling,
   strangulation, the ax, the block, the chair, the gallows,
   the gas chamber, the guillotine, the hot seat, the rope