Pretty self explanatory. A sexual manuever between a guy and a girl. One of the partners performs a crab walk, while the other parter performs a bear walk, they bone in these positions. This makes sex both fun and mobile. A company is designing a harness for this manuever so that it will be easier and less physically strenuous to perform.
"I totally pulled the C-dub B-dub on that girl last night, it was awesome." (the common slang for crab walk bear walk is C-dub B-dub)