blue balls

Short definition from Wiktionary

Noun

1. 1
   A cramp-like ache in the testicles and prostate region caused by prolonged sexual arousal; testicles experiencing such an ache.
2. 2
   Unfulfilled sexual desire.
3. 3
   Buboes (in a person of any sex) caused by a sexually transmitted infection; the infection that causes them.

Verb

1. 1
   third-person singular simple present indicative of blue-ball