Source : Webster's Revised Unabridged Dictionary (1913)

Hypanthium \Hy*pan"thi*um\, n.; pl. L. {Hypanthia}, E.
   {Hypanthiums}. [NL., fr. Gr. "ypo beneath + 'a`nqos flower.]
   (Bot.)
   A fruit consisting in large part of a receptacle, enlarged
   below the calyx, as in the {Calycanthus}, the rose hip, and
   the pear.

Source : WordNet®

hypanthium
     n : the cuplike or ringlike or tubular structure of a flower
         which bears the sepals and stamens and calyx (as in
         Rosaceae) [syn: {floral cup}, {calyx tube}]
     [also: {hypanthia} (pl)]