What does "truffle" mean?

Truffle: Any one of several kinds of roundish, subterranean fungi, usually of a blackish color. The French truffle (Tuber melanosporum) and the English truffle (T. æstivum) are much esteemed as articles of food. Truffle worm (Zoöl.), the larva of a fly of the genus Leiodes, injurious to truffles. Truffle pig, a pig used for finding truffles. Note: When trained, certain pigs have a peculiar ability to smell truffles which lie underground, making them useful for searching out hidden truffles.