A "Lobster Trap" refers to a woman frequently infested with "crabs" and other sexually transmitted external parasites. Alternately, it refers to the genital region of a promiscuous and/or unclean female.
You don't want what she got! She ain't nothin' but a lobster trap!
I gotta hit that! I don't care if she's packing a lobster trap!
The act of pulling one's penis out of a woman's vagina while simmultaneously releasing one's balls from her anal cavity. This in turn makes a suction sound that can quite humorous. The maneuver resembles a lobster (the woman) being caught in a trap (the man) and not being released until the man blows his load and his balls decrease in size allowing the removal from her anus.
"I just lobster trapped that fine specimen. Boyyahh!!"