(getter). (1) In chemistry, any substance added to a system or mixture to consume or inactivate traces of impurities. (2) In metallurgy, an active metal added to a molten metal or alloy that combines with oxygen or nitrogen in the melt and causes its removal into the slag. Alloys including such metals as thorium, zirconium, and cerium as well as carbon and misch metal are used in vacuum tubes to absorb traces of residual gases.