A love of pop culture, especially 60's or 70's era, as well as an appreciation for camp. See Retrosexual.
"I heard Mark bought the complete Brady Bunch series on DVD. Is he gay?" "No, he just has a total retrocrush."
(n.) A brief but intense infatuation with someone from the past, especially someone unattainable or inappropriate.
I have the hugest retrocrush on Marcia from the Brady Bunch! Yeah, I know the character is in high school and I'm in my fifties now, but hey, she was older than me when I was a kid. Don't judge me.