The definition of a synecdoche is a figure of speech using a word that is a part to represent a whole, a whole to represent a part or a material to represent an object.(noun)
An example of a synecdoche is referring to a vehicle as "wheels," one policeman as "the police," cola as "Coke" and credit cards as "plastic."
See synecdoche in Webster's New World College Dictionary
Origin: LME, altered (infl. by L) < synodoche < ML sinodoche, for L synecdoche < Gr synekdochē, lit., a receiving together < synekdechesthai, to receive together < syn-, together + ekdechesthai, to receive < ek-, from + dechesthai, to receive < IE base *de- > decent
See synecdoche in American Heritage Dictionary 4
Origin: Middle English synodoches
Origin: , from Medieval Latin synodoche
Origin: , alteration of Latin synecdochē
Origin: , from Greek sunekdokhē
Origin: , from sunekdekhesthai, to take on a share of
Origin: : sun-, syn-
Origin: + ekdekhesthai, to understand (ek-, out of; see eghs in Indo-European roots + dekhesthai, to take; see dek- in Indo-European roots).