genus Pelargonium ge·nus·pe·largonium uncommon noun 1. geraniums native chiefly to South Africa; widely cultivated SynonymsPelargoniumgenus Pelargonium Related words Broader terms rosid dicot genus Parts Geraniaceae Part of rose geraniumfish geraniumivy geraniumapple geraniumlemon geranium WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.