The Collaborative International Dictionary
Hypocarpium
Hypocarp \Hy"po*carp\, Hypocarpium \Hy`po*car"pi*um\, n. [NL. hypocarpium, fr. Gr. "ypo` beneath + ? fruit.] (Bot.) A fleshy enlargement of the receptacle, or for the stem, below the proper fruit, as in the cashew. See Illust. of Cashew.
Wiktionary
hypocarpium
n. (context botany English) An enlarged fleshy structure that forms below the fruit, from the receptacle or hypanthium.