“The difference is between compulsion of the will (vis compulsiva) which results in an act though not of free volition, and physical compulsion (vis absoluta) in which the unavoidable movement is no act at all.” Rollin M. Perkins & Ronald N. Boyce, Criminal Law 1054–55 (3d ed. 1982).
vis absoluta
vis absoluta (vis ab-s[schwa]-loo-t[schwa]). Physical compulsion.