1a hard, lustrous spherical mass, typically white or bluish-grey, formed within the shell of a pearl oyster or other bivalve mollusc and highly prized as a gem:a linen garment decorated with pearls [mass noun]:necklaces of amethyst and pearl [as modifier]:a pair of pearl earrings
an artificial imitation of a pearl.
(pearls) a necklace of pearls:tweeds look traditional teamed with twinset and pearls
something resembling a pearl:the sweat stood in pearls along his forehead