n. In botany: A dry one-celled seed-vessel consisting of a single carpel, and dehiscent only by the ventral suture, as in the milkweed and larkspur.n. Any bladder-shaped appendage; a utricle.n. In anatomy and zoology, a minute secretory or excretory cavity, sac, or tube; one of the ultimate blind ramifications of a secretory surface; a glandular cul-de-sac; a mucous crypt or lacuna; a minute nodule of lymphoid tissue.n. In entomology, a cocoon; the covering made by a larva for its protection during the pupa state.