hard-on

noun2

1. •
   (slang, vulgar) An erection of the penis.

   • I'm lying here with a hard-on, it's not even 10:00 yet. — 1980
2. •
   (vulgar, figurative) A desirous arousal based on a fascination or obsession.

   • ... and corporations duke it out with the kind of military tactics and apparatus that would give anybody who appreciates the Navy SEALs a hard-on. — 2012