Sacrifice - The voluntary offer of material for the purpose of gaining a more favorable advantage than the material investment. Unlike a combination, a sacrifice is not a cut and dried affair, and there is usually an element of uncertainty associated with it. Though a combination always has one or more sacrifices, a sacrifice need not be associated with a combination.
In his Material Loss and Sacrifice chapter, he notes a few moves from a few games
Selesniev-Alekhine, Triberg 1921, move 20...Rb4
Reshevsky-T.Petrosian, Zurich 1953, move 25...Re6
Taimanov-Karpov, Moscow 1973, beginning with move 17...Rc4