The Collaborative International Dictionary of English v.0.48:
Prevail \Pre*vail"\, v. i. [imp. & p. p. Prevailed; p. pr. &
vb. n. Prevailing.] [F. pr['e]valoir, OF. prevaleir, L.
praevalere; prae before + valere to be strong, able, or
worth. See Valiant.]
1. To overcome; to gain the victory or superiority; to gain
the advantage; to have the upper hand, or the mastery; to
succeed; -- sometimes with over or against.
When Moses held up his hand, Israel prevailed, and
when he let down his hand, Amalek prevailed. --Ex.
So David prevailed over the Philistine. --1 Sam.
This kingdom could never prevail against the united
power of England. --Swift.
2. To be in force; to have effect, power, or influence; to be
predominant; to have currency or prevalence; to obtain;
as, the practice prevails this day.
This custom makes the short-sighted bigots, and the
warier skeptics, as far as it prevails. --Locke.
3. To persuade or induce; -- with on, upon, or with; as, I
prevailedon him to wait.
He was prevailed with to restrain the Earl.
Prevail upon some judicious friend to be your
constant hearer, and allow him the utmost freedom.