The term 'Carpet Fibers' refers to the materials used to make carpets. The most common carpet fibers are nylon, polyester, olefin, and wool. Nylon is a synthetic fiber that is strong and durable, making it a popular choice for carpets. Polyester is also a synthetic fiber that is resistant to stains and fading. Olefin is a synthetic fiber that is lightweight and resistant to moisture and mildew. Wool is a natural fiber that is soft and luxurious, but it is also more expensive than synthetic fibers. The crossword solution for this term is 'ISTLES', which is an acronym for the four main types of carpet fibers: I for Nylon, S for Polyester, T for Olefin, and L for Wool.