The genitals of a drunken woman. Derived from the term "hooch", a slang word for alcohol and "coochie", a slang word for a woman's genitals. The meaning becomes clear when you know the root-words involved.
Frank: "Where's Dave? I thought he was partying with us tonight!"
Jim: "He'll be back in a minute, he's doing the hoochie-coochie."