The Collaborative International Dictionary
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.
Douglas Harper's Etymology Dictionary
"substitute," 1640s, from neuter of Latin succedaneus "succeeding, acting as substitute" (see succeed). Especially of inferior drugs substituted for better ones. Related: Succedaneous.
Wiktionary
n. A substitute, replacement for something else, particularly of a medicine used in place of another.
WordNet
n. (medicine) something that can be used as a substitute (especially any medicine that may be taken in place of another)
[also: succedanea (pl)]
Wikipedia
Usage examples of "succedaneum".
The bark of the willow has, indeed, been justly considered as a succedaneum for Peruvian bark, as has also that of the horse-chestnut tree, the leaf of the holly, the snake-root, etc.