(a) The springing up of water, a gushing, welling forth, or bubbling up of water; ~ up; (b) the act or process of boiling; the boiling up (of a pot filled with liquid); a period of boiling [quot. ?a1425]; also [quot. 1440], glossing L decoctio: the boiling down (of milk or another liquid) to thicken or curdle it; glossing L coagulatio: the curdling or coagulation (of a liquid) as a result of boiling; ~ led, a pot for boiling, cauldron; at ~, at a boil; (c) the act or process of melting metal, casting, founding; also, the tempering (of ingots); ~ togeder; (d) some sort of process undergone by bodily humors, ?morbid 'boiling' or expansion.