1. To bring to, or maintain at, the boiling point, as of water and other liquids
2. To come to the boiling point and change from a liquid to vapor
3. To cook in boiling liquid

A painful sore with a hard pus-filled core; SYN. furuncle.
Small pus-filled swelling originating around a hair follicle or in a sweat gland. Usually caused by local infection with Staphylococcus aureus bacterium, boils are most likely to form if resistance is low or diet inadequate.