Rocky Mountain sheep roc·ky·moun·tainsheep uncommon noun 1. wild sheep of mountainous regions of western North America having massive curled horns Synonymsbighornbighorn sheepcimarronRocky Mountain bighornRocky Mountain sheepOvis canadensis Related words Broader terms mountain sheep Parts Ovis WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.