Webster's Dictionary 
(1): (n.) The bully tree (Minusops globosa); also, its milky juice (balata gum), which when dried constitutes an elastic gum called chicle, or chicle gum.
(2): (n.) A West Indian sapotaceous tree (Bumelia retusa).
The Nuttall Encyclopedia 
A vegetable gum used as a substitute for gutta-percha, being at once ductile and elastic; goes under the name of bully.