veto vs disallow

veto is a noun but disallow is not a noun.

Word	Noun	Adjective	Verb	Adverb
veto	Yes	No	Yes	No
disallow	No	No	Yes	No

As verbs, veto and disallow are synonyms defined as:

Other synonyms of veto include forbid, interdict, nix, prohibit, proscribe.

veto (noun)	disallow (noun)
a vote that blocks a decision
the power or right to prohibit or reject a proposed or intended act (especially the power of a chief executive to reject a bill passed by the legislature)

veto (verb)	disallow (verb)
command against	command against
vote against; refuse to endorse; refuse to assent