1. inert Idle in all uses rests upon its root meaning, as derived from the Anglo-Saxon idel, which signifies vain, empty, useless. Idle thus denotes not primarily the absence of action, but vain action- Synonyms: idle, inactive, inert, slothful, trifling, unoccupied, indolent, lazy, sluggish, unemployed, vacant Antonyms: active, busy, diligent, employed, industrious, occupied, working