The Collaborative International Dictionary of English v.0.48:
Petaloideous \Pet`al*oid"e*ous\, a. (Bot.) Having the whole or part of the perianth petaline. [1913 Webster] Petaloideous division, that division of endogenous plants in which the perianth is wholly or partly petaline, embracing the Liliace[ae], Orchidace[ae], Amaryllide[ae], etc. [1913 Webster]