Defn: To act together; to work in concert; to unite. [Obs.]
But if I tell you how these two did coact. Shak.

COACTION
Co*ac"tion, n. Etym: [L. coactio.]

Defn: Force; compulsion, either in restraining or impelling. Sojth.

COACTIVE
Co*ac"tive, a. Etym: [In sense 1, fr. 1st Coact; in sense 2, fr. 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. With what's unreal thou coactive art. Shak.

COACTIVELY
Co*ac"tive*ly, adv.

Defn: In a coactive manner.

COACTIVITY
Co`ac*tiv"i*ty, n.

Defn: Unity of action.