To counterfeit means to imitate something. Counterfeit products are fake replicas of the real product. Counterfeit products are often produced with the intent to take advantage of the superior value of the imitated product. The word counterfeit frequently describes both the forgeries of currency and documents, as well as the imitations of clothing, handbags, shoes, pharmaceuticals, aviation and automobile parts, watches, electronics (both parts and finished products), software, works of art, toys, movies. Counterfeit products tend to have fake company logos and brands. In the case of goods, it results in patent infringement or trademark infringement. Counterfeit consumer products have a reputation for being lower quality (sometimes not working at all) and may even include toxic elements. This has resulted in the deaths of hundreds of thousands of people, due to automobile and aviation accidents, poisoning, or ceasing to take essential compounds (e.g. in the case a person takes non-working medicine).
“Counterfeit,” Wikipedia, accessed August 13, 2016, https://en.wikipedia.org/wiki/Counterfeit.