1. Full of power; capable of producing great effects of any kind; potent; mighty; efficacious; intense; as, a powerful man or beast; a powerful engine; a powerful argument; a powerful light; a powerful vessel. The powerful grace that lies In herbs, plants, stones, and their true qualities. (Shak)
2. (Science: chemical) large; capacious; said of veins of ore.
Synonym: mighty, strong, potent, forcible, efficacious, energetic, intense.