a colorless or pinkish crystalline alkaloid, CHNO, extracted from the Calabar bean, used in medicine for stimulating intestinal muscles, contracting the pupils of the eyes, etc.
See physostigmine in American Heritage Dictionary 4
(fīˌsō-stĭgˈmēnˌ) also phy·so·stig·min(-mĭn)
noun
A crystalline alkaloid, C15H21N3O2, extracted from the Calabar bean, used in medicine as a miotic and cholinergic agent and to enhance memory in patients with Alzheimer's disease. Also called eserine.