The Collaborative International Dictionary of English v.0.48:

Regma \Reg"ma\ (r?g"m?), n. [NL., fr. Gr. ????, -???, fracture,
   fr. ?????? to break.] (Bot.)
   A kind of dry fruit, consisting of three or more cells, each
   which at length breaks open at the inner angle.
   [1913 Webster]