Real Dictionary

caryopsis in American English
a small, dry, one-seeded fruit in which the ovary wall remains joined with the seed in a single grain, as in barley, wheat, corn, rice, etc.
noun: a small, one-celled, one-seeded, dry indehiscent fruit with the pericarp adherent to the seed coat, the typical fruit of grasses and grains

caryopsis in British English
noun: a dry seedlike fruit having the pericarp fused to the seed coat of the single seed: produced by the grasses