genus Malacothamnus ge·nus·ma·lacothamnus uncommon noun 1. genus of shrubs or small trees: chaparral mallow SynonymsMalacothamnusgenus Malacothamnus Related words Broader terms dilleniid dicot genus Parts Malvaceae Part of chaparral mallow WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.