Petaloideous \Pet`al*oid"e*ous\, a. (Bot.) Having the whole or part of the perianth petaline.

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.

Source: Webster's Revised Unabridged Dictionary (1913)