Occurring by chance. See Synonyms at chance. Occurring at irregular or infrequent intervals; occasional: casual employment at a factory; a casual correspondence with a former teacher. Unpremeditated; offhand: a casual remark. Being without ceremony or formality; relaxed: a casual evening with friends. Suited for everyday wear or use; informal. Not serious or thorough; superficial: a casual inspection. Showing little interest or concern; nonchalant: a casual disregard for cold weather. Lenient; permissive: a casual attitude toward drugs. Not close or intimate; passing: a casual acquaintance with avant-garde music. One that serves or appears at irregular intervals, especially a temporary worker. Casualwear: sent my casuals to the cleaners. A soldier temporarily attached to a unit while awaiting permanent assignment.