Upper Carboniferous period up·per·car·boniferousperiod uncommon noun 1. from 310 million to 280 million years ago; warm climate; swampy land SynonymsPennsylvanianPennsylvanian periodUpper CarboniferousUpper Carboniferous period Related words Broader terms period Parts Carboniferous WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
