1. Not active or tending to be active.
2. 1. Not functioning or operating; out of use: inactive machinery.
   2. Not being in continuous use or operation: an inactive brokerage account.
3. Retired from duty or service.
4. Chemistry Not readily participating in chemical reactions; inert.
5. Biology Marked by the absence or reduction of activity, such as the ability to cause infection.
6. Medicine Quiescent. Used especially of a disease.
7. Physics Showing no optical activity in polarized light.

Synonyms: These adjectives mean not involved in or disposed to movement or activity. Inactive simply indicates absence of activity: retired but not inactive; an inactive factory.
Idle refers to persons who are not doing anything or are not busy: employees idle because of the strike.
It also refers to what is not in use or operation: idle machinery.
Inert describes things powerless to move themselves or to produce a desired effect; applied to persons, it implies lethargy or sluggishness, especially of mind or spirit: "The Honorable Mrs. Jamieson . . . was fat and inert, and very much at the mercy of her old servants" (Elizabeth C. Gaskell).
Passive implies being reactive instead of proactive: "in an hour like this, when the mind has a passive sensibility, but no active strength" (Nathaniel Hawthorne).
Dormant refers principally to a state of suspended activity but often implies the possibility of renewal: dormant feelings of affection.
Torpid suggests sluggishness or apathy: "It is a man's own fault, it is from want of use, if his mind grows torpid in old age" (Samuel Johnson).
Supine implies abject lack of will: "No other colony showed such supine, selfish helplessness in allowing her own border citizens to be mercilessly harried" (Theodore Roosevelt).