1.  citron(n = noun.food) - large lemonlike fruit with thick aromatic rind; usually preserved;
is a kind of citrous fruit, citrus, citrus fruit
is a part of citron, citron tree, citrus medica

2.  citron(n = noun.plant) citron tree, citrus medica - thorny evergreen small tree or shrub of India widely cultivated for its large lemonlike fruits that have thick warty rind;
is a kind of citrus, citrus tree
has parts: citron

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. [1913 Webster]

2.  A citron tree, Citrus medica. [1913 Webster]

3.  A citron melon. [1913 Webster]

citron, n.
1 a shrubby tree, Citrus medica, bearing large lemon-like fruits with thick fragrant peel.
2 this fruit.

Etymology:
F f. L CITRUS, after limon lemon

citron tree