Definition of locust tree:
(n) :
A honey locust (Gleditsia triacanthos), a leguminous tree with pods having a sweet, edible pulp.
(n) :
A black locust (Robinia pseudoacacia), a leguminous tree with toxic pods, but useful for making honey.
(n) :
A carob tree (Ceratonia siliqua).
(n) :
Any of a number of similar looking trees in the genera Gleditsia and Robinia.
(n) :
(less common) An African locust bean tree (Parkia biglobosa).