Dictionary.net

two words that can be interchanged in a context are said to be synonymous relative to that context

two words that can be interchanged in a context are said to be synonymous relative to that context

One of two or more words (commonly words of the same language) which are equivalents of each other; one of two or more words which have very nearly the same signification, and therefore may often be used interchangeably. See under Synonymous.

A word having the same or nearly the same meaning as another, as sharp and keen.

A word having the same meaning with another.

A word having the same, or nearly the same, meaning as some other; one of two or more words that have one or more meanings in common, but otherwise differ. synonyme.

A word which has the same meaning as another word.

n. [Greek] One of two or more words in the same language which are the equivalents of each other, or which have very nearly the same signification, and therefore are liable to be confounded together ;- also synonyme, synonymon.