The act of placing one's genitalia in on or around a woman's mouth as she is crawling on her hands and feet while facing upwards in what is commonly known as a crab walk. It is the male's responsibility to repetitively slap his penis on the said woman's forehead and keep his testicles in her mouth as she desperately tries to free herself by crabwalking away.
John: Hey Becky how long can you hold the crabwalk position?
Becky: I don't know like five minutes.
John: Do you want to go Crab bagging with me?
Becky: What's that?