The term "clotheshorse" or "clothes horse" actually has two different meanings, depending on the context. One meaning refers to a laundry accessory, while the other is an adjective for a stylish person. The adjective was derived from the noun, since both seem to exist solely for the purpose of displaying clothes. A laundry clotheshorse can be purchased from a laundry supply, and a human clotheshorse can probably be observed in the wild if you wait long enough at a bar, coffeehouse, or fashionable restaurant.
In laundry terms, a clotheshorse is a drying rack. The clotheshorse is designed to be folded when it is not needed, and unfolded to reveal an assortment of dowels on which clothing can be hung to dry. For hand washed clothing and delicates, a clotheshorse is a vitally necessary tool. It can also be useful to keep one around for drying sweaters and coats which have been soaked in the rain. Generally, a clotheshorse is kept in the laundry room or another location with a linoleum or tile floor, so that dripping water from the drying clothes does not damage the flooring.
Most typically, a laundry clotheshorse is made of wood. This unfortunate design decision means that it is occasionally necessary to bleach the clotheshorse or expose it to bright sunlight to remove mold and mildew. Variants made from metal and plastic are also available, although these construction materials have their shortcomings as well. Make sure to oil or wax the joints of a clotheshorse regularly to keep it moving smoothly.
A human clotheshorse is someone who puts a great deal of energy into dressing fashionably. The term is often applied to a vain person who invests sometimes alarming amounts of time and money in looking good. Being a clotheshorse can cost a great deal of money, as changes in style may necessitate an entirely new wardrobe. Because dressing fashionably requires good taste, lots of time, a fair amount of money, and the willingness to follow trends, it is not for the faint of heart. The term may also be used less pejoratively to simply describe someone who dresses smartly.
Some people use the more negative term "clothes whore" to refer to a clotheshorse. The term could be viewed either as a mondegreen or a natural evolution of the clotheshorse. It is much more common for someone to refer to him or herself as a clothes whore, often self-deprecatingly. Generally, one should know someone rather well before calling them a clothes whore, as the term is rather denigrating.