The adj casual has 9 senses (first 5 from tagged texts)
1. (3) casual, insouciant, nonchalant -- (marked by blithe unconcern; "an ability to interest casual students"; "showed a casual disregard for cold weather"; "an utterly insouciant financial policy"; "an elegantly insouciant manner"; "drove his car with nonchalant abandon"; "was polite in a teasing nonchalant manner")
2. (2) casual -- (without or seeming to be without plan or method; offhand; "a casual remark"; "information collected by casual methods and in their spare time")
4. (1) accidental, casual, chance -- (occurring or appearing or singled out by chance; "their accidental meeting led to a renewal of their friendship"; "seek help from casual passers-by"; "a casual meeting"; "a chance occurrence")
5. (1) casual, cursory, passing, perfunctory -- (hasty and without attention to detail; not thorough; "a casual (or cursory) inspection failed to reveal the house's structural flaws"; "a passing glance"; "perfunctory courtesy")
6. casual, occasional -- (occuring from time to time; "casual employment"; "a casual correspondence with a former teacher"; "an occasional worker")
7. fooling, casual -- (characterized by a feeling of irresponsibility; "a broken back is nothing to be casual about; it is no fooling matter")
8. free-and-easy, casual -- (natural and unstudied; "using their Christian names in a casual way"; "lectured in a free-and-easy style")
9. casual, effortless -- (not showing effort or strain; "a difficult feat performed with casual mastery"; "careless grace")