From Longman Dictionary of Contemporary Englishfor funfor fun (also just for the fun of it) if you do something for fun, you do it because you enjoy it and not for any other reason I simply believe that killing animals for fun is wrong. Like most people her age, Deborah struck up relationships just for the fun of it. → fun
Examples from the Corpus
for fun• Encourage your child to read all kinds of books for fun.• When we started our band we played music in restaurants just for fun.• We just play poker for fun , not for money.• I only really started the shop for fun, but it's been a huge success. 