boilboilboilsboiledboilingverb (boils, boiling, boiled)1When a liquid boils, it becomes very hot and makes steam and bubbles: Water boils at 100° C.2to heat a liquid until it boils: I boiled some water for the pasta.3to cook something in boiling water: Boil the rice in a pan.a boiled eggboil overto boil and flow over the sides of a pan: Don't let the milk boil over.