The Collaborative International Dictionary of English v.0.48:
Indehiscent \In`de*his"cent\, a. [Pref. in- not + dehiscent: cf. F. ind['e]hiscent.] (Bot.) Remaining closed at maturity, or not opening along regular lines, as the acorn, or a cocoanut. [1913 Webster]WordNet (r) 3.0 (2006):
indehiscent adj 1: (of e.g. fruits) not opening spontaneously at maturity to release seeds [ant: dehiscent]