n. A unit of thermal capacity variously defined as the equivalent of the gram-calory, the kilogram-calory and one thousand kilogram-calories. Of these values the one commonly accepted is that which makes the therm equal to one gram-calory.n. See tharm.n. A hot bath; by extension, any bath or pool.n. In physics, a thermal unit, the water-gram-degree or (small) calory, the amount of heat required to raise one gram of water at its maximum density through one degree centigrade.