- any implement, instrument, or utensil held in the hand and used to form, shape, fasten, add to, take away from, or otherwise change something by cutting, hitting, digging, rubbing, etc.: knives, saws, hammers, shovels, rakes, etc. are tools
- any similar instrument that is the working part of a power-driven machine, as a drill, band-saw blade, etc.
- the whole machine; machine tool
- anything that serves in the manner of a tool; a means: books are a scholar's tools
- a person used to accomplish another's purposes, esp. when these are illegal or unethical; dupe; stooge
- Slang the penis: somewhat vulgar
- Law any instrument or device necessary to one's profession or occupation
ME toole < OE tol, akin to ON tol < ? IE base *deu- > taw