Force; power. Vis inertioe, the resistance in a body to change either its state of rest or state of motion; inert state or unwillingness to change a habit. Vis viva, living force, or kinetic energy. Vis mortua, dead force, or force doing no work.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
In mech., force; power.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)

Usage examples:

He has no real peace of mind, no content, no unalloyed joy, for even in his hours of pleasure, of recreation, of expected jollity he is worrying lest someone is trying to get ahead of him, his vis a- vis is " jollying" him, his partner at golf is trying to steal a march on him, he is not being properly served at the picnic, etc.
- Quit Your Worrying! by George Wharton James
Having placed the nose of the lizard vis a- vis with his own, he opened his jaws to their full extent, took in the head, and commenced gradually sucking the body down his throat.
- The Boy Hunters by Captain Mayne Reid
What government can do, therefore, is to maintain such institutions as may strengthen the vis medicatrix, or desire to better our condition, which poor laws had directly tended to weaken.
- Studies in Literature and History by Sir Alfred Comyn Lyall