Succedaneum \Suc`ce*da"ne*um\, n.; pl. Succedanea. [NL. See Succedaneous.]

One who, or that which, succeeds to the place of another; that which is used for something else; a substitute; specifically (Med.), a remedy used as a substitute for another.

In lieu of me, you will have a very charming succedaneum, Lady Harriet Stanhope. --Walpole.

Source: Webster's Revised Unabridged Dictionary (1913)