Gaining the advantage or superiority; predominant; most common or general.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (adjective, noun) (a. / n.) (adjective / noun)
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (adjective) (adj.) (adjective)
Superior in power; having efficacy; predominant; prevalent.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (adjective) (adj.) (adjective)
Having great power: efficacious: most general.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (adjective) (adj.) (adjective)

Usage examples:

There was, for instance, nothing like an equal and generally recognised ratio of value between gold and silver prevailing at any one single point of time.
- The History of Currency, 1252 to 1896 by William Arthur Shaw
These words so fell in with the prevailing mood of his mind, that having gathered them, they grew upon him, and as he pondered them, he sat gazing out on the bright blowing autumn day.
- Malcolm by George MacDonald
After the road crosses the Rainier Fork, noble fir and amabilis fir appear, but the Douglas fir and western hemlock are still the prevailing species.
- The Forests of Mount Rainier National Park by Grenville F. Allen