Verb (5-dan, ぶ, intransitive)
1.  to play (games, sports);  to enjoy oneself;  to have a good time
2.  to mess about (with alcohol, gambling, philandery, etc.)
3.  to be idle;  to do nothing;  to be unused
4.  to meet up (with friends);  to hang out
5.  to give oneself up (to gambling, drinking, etc.)
6.  to go to (for pleasure or for study)
as 〜に遊ぶ
7.  to tease (somebody);  to play (with)
8.  to intentionally throw a ball to lower the batter's concentration