1 automatic, automated, machine-driven; machine-made:
Early mechanical toys are sometimes quite intricate. This is a mechanical, not a hand-crafted device
2 automatic, reflex, involuntary, instinctive, routine, habitual, unconscious, perfunctory, machine-like, robot-like:
Good manners ought to be mechanical. Blinking is a mechanical reaction to bright light.
3 impersonal, distant, cold, matter-of-fact, unfeeling, insensible, ritualistic, lifeless, spiritless, dead, inanimate, unanimated, unemotional, unartistic, mechanistic, colourless, uninspired, business-like:
The girl at the check-out gave us a mechanical smile.