One who declines or refuses; a dissentient; also = decliner, n. 2. Obsolete.

A person who disagrees with orthodox opinion on religious matters; a dissenter. Obsolete.

One who differs or disagrees in opinion; one who differs from the opinion of the majority.

a person who disassents.

One who dissents in any matter: one who disagrees with any opinion, resolution, or proposal; a dissentient.

One who disagrees; a dissentient.

A person who habitually disagrees or contradicts, esp. one who is deliberately obstructive. Cf. yes-man, n.