casual
adjective
marked by blithe unconcern
“an ability to interest casual students”
“showed a casual disregard for cold weather”
without or seeming to be without plan or method; offhand
“a casual remark”
“information collected by casual methods and in their spare time”
appropriate for ordinary or routine occasions
“casual clothes”
“everyday clothes”
occurring or appearing or singled out by chance
“seek help from casual passers-by”
“a casual meeting”
Synonymschancehasty and without attention to detail; not thorough
“a casual (or cursory) inspection failed to reveal the house's structural flaws”
“a passing glance”
occurring on a temporary or irregular basis
“casual employment”
“a casual correspondence with a former teacher”
Synonymsoccasionalcharacterized by a feeling of irresponsibility
“a broken back is nothing to be casual about; it is no fooling matter”
Synonymsfoolingnatural and unstudied
“using their Christian names in a casual way”
“lectured in a free-and-easy style”
Synonymsfree-and-easynot showing effort or strain
“a difficult feat performed with casual mastery”
“careless grace”
Synonymseffortless
Source: WordNet 3.1, Princeton University