When a guy and a girl are not dating but are together. They are exclusive, in other words, they like each other enough to only hook up with each other. Usually after a succesful hookupship, the two people begin dating. There has only been one succesful hookupship in the whole history of the universe so far, and I hear the people were pretty saweet.
Guy: Are you and Emma dating?
Other guy: Naw man, we're in a hookupship.
GuyL: Sweet dude, keepin' it single! Now you can totally hook up with Penelope at that party on Saturday!
Other guy: NO DUDE, didn't you get what I said, we're in a hookupSHIP
(this conversation is completely fictional..since there's only been one succesful hookuship and it's not laura and this guy.)