tree onion treeo·nion uncommon noun 1. type of perennial onion grown chiefly as a curiosity or for early salad onions; having bulbils that replace the flowers Synonymstree onionEgyptian oniontop onionAllium cepa viviparum Related words Broader terms onion WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
