n. The undissolved solids which settle to the bottom of the tank in which animal garbage is boiled with water, the grease being removed by skimming and the tank-water drawn off. (See tank-water.) Tankage is used in the manufacture of mixed fertilizers.n. The act or process of storing oil, etc., in a tank; also, the price charged or paid for storage in a tank; the capacity of a tank or tanks; quantity, as of oil, that may be in a tank or tanks.n. The waste residue deposited in lixiviating-vats or in tanks in which fat is rendered. The latter product, dried, is much used as a fertilizer.