A person who appraises the works of others.
A specialist in judging works of art.
An opponent.
One who criticizes; a person who finds fault.
One who writes glosses.
A legal scholar of the Middle Ages, (specifically) one who authored glosses on legal texts (especially the Corpus Juris of Justinian), typically distinguished from the later commentators who wrote in extended prose and adopted a more pragmatic form of jurisprudence.