casual

Concise Oxford English Dictionary © 2008 Oxford University Press:
casual /ˈkaʒjʊəl, -zj-/

▶adjective

• 1 relaxed and unconcerned.

  ■ made, done, or acting without much care or thought: a casual remark.

• 2 not regular or firmly established.

  ■ (of a worker) employed on a temporary or irregular basis.

  ■ (of a sexual relationship or encounter) occurring between people who are not established sexual partners.

• 3 happening by chance; accidental: a casual meeting.

• 4 without formality of style, manner, or procedure.

▶noun

• 1 Brit. a casual worker.

• 2 (casuals) clothes or shoes suitable for everyday wear rather than formal occasions.

• 3 Brit. a youth belonging to a subculture characterized by the wearing of expensive casual clothing.

– derivatives
casually adverb,
casualness noun.

– origin ME: from OFr. casuel and L. casualis, from casus ‘fall’.