King James Dictionary 
Pow'Erful, a. Having great physical or mechanical power strong forcible mighty as a powerful army or navy a powerful engine.
1. Having great moral power forcible to persuade or convince the mind as a powerful reason or argument. 2. Possessing great political and military power strong in extent of dominion or national resources potent as a powerful monarch or prince a powerful nation. 3. Efficacious possessing or exerting great force or producing great effects as a powerful medicine. 4. In general, able to produce great effects exerting great force or energy as a powerful eloquence.
The word of God is quick and powerful. Hebrews 4
5. Strong intense as a powerful heat or light.
Webster's Dictionary 
(1): ( a.) Large; capacious; - said of veins of ore.
(2): ( a.) 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.