A sexual act where both the vagina and cervix are penetrated.
In anal sex, this can also be when both the anus and the Houston valves are penetrated.
Also referred to as double dipping
If you don't know what the Houston valves are and are too dumb to figure it out, please consult Google.
His dick was so long he was able to double dock his shawty
You know you have a big dick if you can Double Dock
His dick is so big, it's a double docker