happening by chance; fortuitous

a casual meeting.

without definite or serious intention; careless or offhand; passing

a casual remark.

seeming or tending to be indifferent to what is happening; apathetic; unconcerned

a casual, nonchalant air.

appropriate for wear or use on informal occasions; not dressy

casual clothes; casual wear.

irregular; occasional

a casual visitor.

accidental

a casual mishap.

Obsolete . uncertain.

a worker employed only irregularly.

a soldier temporarily at a station or other place of duty, and usually en route to another station.

adverb

unintentionally , by chance , inadvertently , indifferently , unconcernedly , coolly , unemotionally , reservedly , offhandedly , carelessly , informally , lackadaisically , aimlessly , inconstantly , randomly , haphazardly