A booty call is an informal arrangement between two people to meet up for a late-night sexual encounter. It typically involves two people who have a casual relationship and want to enjoy physical intimacy without any further commitment or expectation of a relationship. A late-night rendezvous, on the other hand, can be more serious and involve romantic intentions. This could include anything from going out for dinner or drinks to spending time together in an intimate setting with the intention of exploring a potential relationship.