citron
cit.ron \'si-tr*n\ n [ME, fr. MF, fr. OProv, modif. of L citrus citron tree] 1a: the fruit of a tree (Citrus medica) like the lemon in appearance and structure but larger; also : this tree 1b: the preserved rind of the citron used esp. in fruitcake 2: a small hard-fleshed watermelon used esp. in pickles and preserves