1 utensil, implement, instrument, device, apparatus, appliance, contrivance, aid, machine, mechanism, gadget, Colloq contraption, gimmick, Chiefly US and Canadian gismo or gizmo:
The work would go faster if you had the proper tools.
2 means, way, agency, weapon, medium, vehicle, instrumentality, avenue, road:
Education is the tool you need to get anywhere in life.
3 puppet, cat's-paw, pawn, dupe, Slang stooge, sucker:
I had been used merely as a tool in her ambitious rise to the top.
4 work, carve, cut, embellish, decorate, ornament, dress, shape:
This is the shop where the leather is tooled and gold-stamped.