MEMBRANA'CEOUS, adjective Belonging to a membrane; consisting of membranes; as a membraneous covering. Birds of prey have membranaceous stomachs, not muscular. 1. In botany, a membranaceous leaf has no distinguishable pulp between the two surfaces. In general, it denotes flatted or resembling parchment.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI