wet dream

Short definition from Wiktionary

Noun

1. 1
   An erotic dream (imaginary vision while sleeping) bringing the sleeper to orgasm.
2. 2
   The orgasm in such a dream.
3. 3
   An exciting fantasy; a very appealing, ideal thing, person, or state of affairs.

Verb

1. 1
   To produce fluids from the sex organs as a result of sexual arousal during sleep; to have an erotic dream; (figurative) to fantasize (about something, especially in a sexual way).
2. 2
   To have an erotic dream about (someone or something); (figurative) to fantasize about (someone or something) sexually.