Counterfeit means made as an illegal fake copy of the real branded thing. Counterfeit notes, counterfeit goods, a counterfeit passport.
The difference from an imitation is the intent to deceive — a copy sold as a copy is not counterfeit. Banknotes carry watermarks, threads and raised print because each is easy to check and hard to reproduce. The word is literally made against.
1adjectivecounterfeitMade as an illegal fake copy.
“The shopkeeper refused the note because he thought it was counterfeit.”
counterfeit is a quality of fakery.
Old French contrefait means made against or imitated, from Latin contra, against, plus facere, to make.
Middle English
countrefet
English, today
counterfeit
From Middle English countrefet. From Middle English counterfeit, countrefet, from Anglo-Norman countrefait, from Old French contrefait, from Latin contra- (“against”) + Latin facere (“to make”). contrafactum.
Etymology from Wiktionary, CC BY-SA