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.
(..) L.T? At the line of march, --. And just for shits and giggles, let's switch to five for tactical traffic. Maintain casual dialogue on assigned channels. Slovnik, take us to --. Cortez, move out. Move out. Let's go. (..)1997 G.I. Jane