A sexual fantasy or erotic fantasy is a mental image or pattern of thought that stirs a person’s sexuality and can create or enhance sexual arousal. A sexual fantasy can be created by the person’s imagination or memory, and may be triggered autonomously or by external stimulation such as erotic literature or pornography, a physical object, or sexual attraction to another person. Anything that may give rise to a sexual arousal may also produce a sexual fantasy, and sexual arousal may in turn give rise to fantasies. (Wikipedia)
