To swoop or plunge, as a bird upon its prey; to fall suddenly; to rush with speed; to make a sudden attack. For then I viewed his plunge and souse Into the foamy main. (Marston) Jove's bird will souse upon the timorous hare. (J. Dryden. Jr)
Origin: Probably fr. OF. Sors, p.p. Of sordre to rise, and first used of an upward swood, then of a swoop in general, but also confused with Souse, See Source.