Descriptive fair use means the use of a word or phrase to describe a product or service, not as a source identifier. For example, a seller of pillows might use the word “soft” to describe them even if someone else is using SOFT as a trademark for pillows. Saying, “Our company’s pillows are soft” would be fair use because in this context the word is being used as an adjective, not as a source identifier. The company probably could not invoke the fair use defense, however, if it were to affix “Soft Pillow” labels to them, if another company is using SOFT as a trademark for pillows.