1. diligent Active refers to both quickness and constancy of action; in the former sense it is allied with agile, alert, brisk, etc.; in the latter, with busy, diligent, industrious. The active l Synonyms: active, agile, energetic, officious, sprightly, alert, expeditious, prompt, spry, brisk, industrious, quick, supple, bustling, lively, ready, vigorous, busy, mobile, restless, wide awake, diligent, nimble Antonyms: dull, inactive, lazy, slow, heavy, indolent, quiescent, sluggish, idle, inert, quiet, stupid