Citron \Cit"ron\ (s[i^]t"r[u^]n), n. [F. citron, LL. citro, fr. L. citrus citron tree (cf. citreum, sc. malum, a citron), from Gr. ki`tron citron]

1. (Bot) A fruit resembling a lemon, but larger, and pleasantly aromatic. The thick rind, when candied, is the citron of commerce.

2. A citron tree.

3. A citron melon.

Citron melon.
   (a) A small variety of muskmelon with sugary greenish flesh.
   (b) A small variety of watermelon, whose solid white flesh is used in making sweetmeats and preserves.

Citron tree (Bot.), 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.

Source: Webster's Revised Unabridged Dictionary (1913)