It can be near impossible to know what to call the person you're "seeing" read: sleeping with but not really "dating" read: attending family functions with. Are they your boo? Your date? Your "special friend? A casual hookup is a sexual relationship that only exists for fulfilling sexual needs. Whether you slept with a cutie one time and have no intentions of doing it again or you plan on getting frisky often but are set in keeping things purely physical, you may be clear on the fact that you're in a casual hookup situation. A casual hookup can be a relationship based in getting it on with a boo, without any other expectations.