Webster's Revised Unabridged Dictionary · 1913

Oppugn

Oppugn , transitive verb

[Old French oppugner, Latin oppugnare; ob (see Ob-) + pugnare to fight. See Impugn.]

To fight against; to attack; to be in conflict with; to oppose; to resist.
They said the manner of their impeachment they could not but conceive did oppugn the rights of Parliament. — Clarendon