Webster's Revised Unabridged Dictionary · 1913

Synonymous

Synonymous , adjective

[Greek {not transcribed}; sy`n with, together + {not transcribed}, {not transcribed}, name. See Syn-, and Name.]

Having the character of a synonym; expressing the same thing; conveying the same, or approximately the same, idea.
These words consist of two propositions, which are not distinct in sense, but one and the same thing variously expressed; for wisdom and understanding are synonymous words here. — Tillotson