reˈheater [f. reheat v. + -er1.] An apparatus for reheating. 1875R. F. Martin tr.Havrez' Winding Mach. 98 Boilers consisting of heaters and reheaters.1897Columbus (Ohio) Disp. 7 Apr. 9/3 The result showed that when the reheater was used a much greater amount of work was performed.