from
The Collaborative International Dictionary of English v.0.48
Jalap \Jal"ap\, n. [F., fr. Sp. jalapa; -- so called from
Jalapa, a town in Mexico, whence it was first obtained.]
(Med.)
The tubers of the Mexican plant {Ipom[oe]a purga} (or
{Exogonium purga}) of the family {Convolvulaceae}, a climber
much like the morning-glory. The abstract, extract, and
powder, prepared from the tubers, are well known purgative
(cathartic) medicines, and are also called jalap. Other
species of {Ipom[oe]a} yield several inferior kinds of jalap,
as the {Ipom[oe]a Orizabensis}, and {Ipom[oe]a tuberosa}.
[1913 Webster]
{False jalap}, the root of {Mirabilis Jalapa}, four-o'clock,
or marvel of Peru.
[1913 Webster]