Trademark law, a test used to determine whether the use of a mark would conflict with another mark that has been registered trade mark. Whether it is likely that the marketplace would confuse the origin of a product or service as being that of a second comer. For example, whether a new comer using the mark Coke Cola would cause confusion in the marketplace so that purchasers would think it is a product actually being produced by Coca-Cola, given the substantial similarity of the names.