Definition of "unimpeachable"

“Patriotism” makes for a slogan that is so unimpeachable it’s arguably even manipulative; as a matter of strategy, it’s harder for opponents to vote against the USA PATRIOT Act than, say, the Enhanced Security Act.

2022 November 12, Matteo Wong, “How Did America End Up With the Z.O.M.B.I.E. Act?”, in The Atlantic‎