An Etymological Dictionary of Astronomy and Astrophysics

1. Being in a state of action; not quiescent.
   

2. Functioning or capable of functioning.
   

3. Marked by vigorous activity.

Etymology (EN): M.Fr. actif, from L. activus, from actus, p.p. of agere, → act.

Etymology (PE): Žirâ, adj. from stem žir, → act + suffix -â.