From The Collaborative International Dictionary of English v.0.48 [gcide]:
Betel \Be"tel\ (b[=e]"t'l), n. [Pg., fr. Tamil ve[.t][.t]ilei,
prop. meaning, a mere leaf.] (Bot.)
A species of pepper (Piper betle), the leaves of which are
chewed, with the areca or betel nut and a little shell lime,
by the inhabitants of the East Indies. It is a woody climber
with ovate many-nerved leaves.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
betel
n 1: Asian pepper plant whose dried leaves are chewed with betel
nut (seed of the betel palm) by southeast Asians [syn:
betel, betel pepper, Piper betel]