An acronym that stands for "Herpes is for life". The addition of "bro" at the end is optional. The phrase originated from the movie "Pineapple Express".
Saul: Herpes is for life (HIFL), bro!
Red: Yeah, well, I'm gonna try to definitely put some sort of medical ointment on it. I've been takin Vicodin; that really doesn't take down the swelling, though.