Citron /(sĭt"rŭn)/

Cit·ron

Citron

n.
  1. A fruit resembling a lemon, but larger, and pleasantly aromatic; it is produced by the citron tree (Citrus medica). The thick rind, when candied, is the citron of commerce. The fruit was once called the lime. (Bot)
  2. A citron tree, Citrus medica.
  3. A citron melon.

Phrases & Compounds
Citron melon
A small variety of muskmelon with sugary greenish flesh.
Citron tree
the tree which bears citrons. It was probably a native of northern India, and is now understood to be the typical form of Citrus Medica.