Aginer (noun) (US informal)
a-gina
A person who is against something; one who opposes a proposal, course of action, point of view, etc. Also more generally: a person having a habitually negative attitude; one who opposes any change as a matter of principle.
Early 20th century; earliest use found in Westminster (Philadelphia). From agin, regional and colloquial variant of again + -er.
Example sentences
“He’s such an aginer, he opposes everything.”