They are only 'casual' acquaintances. [=they know each other but not very well]
She takes a 'casual' [='nonchalant'] approach to her homework.
He was dressed 'casually' in jeans and a sweatshirt.
(..) im an asshole, i know that. it worked for me in highschool. and its been a reflex ever since Lori, the worst that can happen is you go on a fun casual date, with a guy who just wants to prove that he can be something more than a jerk plus you are a huge catch, and its fuck it, fine (..)2012 Ted