Powerful, a.
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. (Mining)
Large; capacious; -- said of veins of ore.
Syn. -- Mighty; strong; potent; forcible; efficacious; energetic; intense. -- Pow"er*ful*ly, adv. -- Pow"er*ful*ness, n.
Shades of meaning
Fernald lists powerful only as an antonym, under vain.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given