Definition: (1) Made or used as a substitute, typically an inferior one, for something else; (2) not genuine or real
“How can your romance hope to be the veil of an ersatz human nature?”
—“The Surface of Me”–bonus track on Japanese version of The Empire Strikes First
In a sentence: While some of the students on the trip to Washington, D.C. enjoyed the White House or the Jefferson Memorial best of all, others rejoiced at the cheap, ersatz Ray Bans sold on the street. Lookin’ sharp, Jared.
Synonyms: fraudulent, fake, counterfeit, bogus
Antonyms: real, genuine, authentic, straight legit
sources: wikipedia, the google, merriam-webster.com