odd, unmatched, unmated, unpaired(adj)

of the remaining member of a pair, of socks e.g.

matchless, nonpareil, one(a), one and only(a), peerless, unmatched, unmatchable, unrivaled, unrivalled(adj)

eminent beyond or above comparison

"matchless beauty"; "the team's nonpareil center fielder"; "she's one girl in a million"; "the one and only Muhammad Ali"; "a peerless scholar"; "infamy unmatched in the Western world"; "wrote with unmatchable clarity"; "unrivaled mastery of her art"

unmatched(Adjective)

not matched; odd

unmatched(Adjective)

peerless; unrivalled; beyond comparison