Refers to the attractiveness rating scale of 1-10. "10" being the rating and "hard" designating that the person being rated is solidly, without doubt deserving of that rating. Hard can be used as the prefix to any of the 1-10 numbers. Its opposite being "soft 10"
Dang, see that girl over there? That booty makes her a hard 10 for sure!
by ajs11 December 01, 2013