Planning to have sex with, or having had sex with a person of either gender (despite the phallic imagery) from Australia.
i.e. to "poke" a "roo", "roo" being used as a short form for "kangaroo" and a slang for someone from Australia
Usually used in clubs, or nights out in public areas or tourist spots where one might find a large number of Australians.
"I'm going to Pokaroo"
"Are you going to pokaroo tonight?"
or looser uses of the term such as:
"I'm going to poke that roo", or "I poked that roo"