a.
1.
Operative, operant, influential, efficient, effective, effectual, efficacious, living, vigorous, in action, in operation, in actual process, in force, in vitality, valid.
2.
Busy, diligent, assiduous, industrious, indefatigable, unremitting, laborious, sedulous, notable, at work, hard at work, diligently employed, busily engaged.
3.
Alert, nimble, agile, supple, brisk, dapper, stirring, smart, quick, prompt, ready, lively, sprightly, spirited. See spry .
4.
Enterprising, energetic, strong, efficient, in earnest, vigorous, full of life, animated, ebullient, fervent.
5.
Drastic ( as medicine ), powerful, potent, effective, efficacious.
6.
( Gram. ) Transitive.