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