When you are going down on a woman and discover she is on the rag and has a tampon string hanging out (see "ripcord"). Determined to eat her out, you take the string in your mouth and bite down, ripping it out with your teeth. After thrashing it back and forth a bit, you fling it over one shoulder with your mouth. In order to properly complete the shark bite, you must proceed with performing oral sex on the woman.
I discovered she was on the rag, but wanted to eat her out anyway. My only choice was to give her a shark bite. Boy, was she surprised.