rank has 21 distinct synonyms spread across 7 of its 13 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a row or line of people (especially soldiers or police) standing abreast of one another
“the entrance was guarded by ranks of policemen”
the ordinary members of an organization (such as the enlisted soldiers of an army)
“the strike was supported by the union rank and file”
position in a social hierarchy
“the British are more aware of social status than Americans are”
the body of members of an organization or group
“they polled their membership”
complete and without restriction or qualification; sometimes used informally as intensifiers
“absolute freedom”
assign a rank or rating to
“how would you rank these students?”
3 of the 13 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for rank.
Synonyms, antonyms and the broader and narrower relations for rank come from Princeton University’s WordNet. Full sources and licences.