Second hand semi

When a friend tells you of his/her recent sexcapades in such graphic detail that it results in you getting half a boner

Friend 1 - "Maaaate, Amber right... gives the best blowjobs eveeer. Sloppy, great d control, eye contact...all the way in (and so on)"

Friend 2 "Mate, I'm not sure sure if I should admit this, but that description has just given me a a second hand semi"