ambrosia beetle Syllabification: (am·bro·sia bee·tle)Definition of ambrosia beetle noun a small dark wood-boring beetle, the adults and larvae of which feed on a fungus that they cultivate, called ambrosia. Genus Platypus (family Platypodidae), and Xyleborus and other genera (family Scolytidae) ambrosia beetle in other Oxford dictionaries Definition of ambrosia beetle in the British & World English dictionary