The Collaborative International Dictionary of English v.0.48:

Veto \Ve"to\, v. t. [imp. & p. p. Vetoed (v[=e]"t[=o]d); p.
   pr. & vb. n. Vetoing.]
   To prohibit; to negative; also, to refuse assent to, as a
   legislative bill, and thus prevent its enactment; as, to veto
   an appropriation bill.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "vetoed":
   banned, barred, contraband, forbade, forbid, forbidden, illegal,
   illicit, nonpermissible, not permitted, off limits, out of bounds,
   outlawed, prohibited, ruled out, taboo, tabooed, unallowed,
   unauthorized, under the ban, unlawful, unlicensed, unpermissible,
   unsanctioned, untouchable, verboten