Co·ac'tive adjective [ In sense 1, from 1st Coact ; in sense 2, from 2d Coact .] 1. Serving to compel or constrain; compulsory; restrictive. « Any coactive power or the civil kind. Bp. Warburton. » 2. Acting in concurrence; united in action. ... Found on http://www.encyclo.co.uk/webster/C/98