(1):

(a.) Destitute of the power of moving itself, or of active resistance to motion; as, matter is inert.

(2):

(a.) Indisposed to move or act; very slow to act; sluggish; dull; inactive; indolent; lifeless.

(3):

(a.) Not having or manifesting active properties; not affecting other substances when brought in contact with them; powerless for an expected or desired effect.