Obviously of a sexual nature, Arcturian is just probably a reference to the world where the marines received said poontang. Maybe the locals had some unusual sexual practices?
Must've been unusual if the sex of the hooker didn't really matter.
It could even be that they were not human, Cameron does allude to the existence of other alien races with little things like the 'Bug Stompers' icon the marines on the Sulaco use.
I don't think it was ever specified, it was just put in there to make the marines seem like they'd been together for a long time, and maybe show that they were pretty close friends, not to expand the 'lore' of the Alien universe, as it were.