There are certain parts of the anatomy that change texture based on sexual arousal. And despite the fact that nipples are often compared to pebbles and cocks to rocks, HUMAN FLESH DOES NOT ACTUALLY GET THAT HARD.
There's a bit of ladies' cooking wisdom I ran across while learning my way around the kitchen -- "When a chicken breast has about the same texture as an erect penis, it's done."
Context contains more ROCK HARD lulz. Flocked to the comm, but QWP.