1to play (games, sports); to have fun or enjoy oneself
子供たちが公園で元気に遊んでいる。
The children are playing energetically in the park.
週末は友達とカードゲームで遊んだ。
I played card games with friends over the weekend.
猫が紐で遊んでいる。
The cat is playing with a string.
仕事の後にテニスで遊ぶのはいい運動だ。
Playing tennis after work is good exercise.
2to mess about with (alcohol, gambling, etc.); to dabble in indulgent or risky pastimes
彼は賭け事で遊びすぎて借金を作った。
He gambled too much and ran up debts.
休日に軽く酒で遊ぶ程度なら問題ない。
Drinking casually on days off isn't a problem.
若い頃は女性関係で遊んでいたと本人が認めている。
He himself admits that he used to fool around with women when he was young.
3to be unused or lie idle; to be left unutilized; also to be idle/do nothing
彼の才能を遊ばせておくのはもったいない。
It's a waste to leave his talent unused.
古い機械が工場の片隅で長い間遊んでいる。
The old machine has been sitting unused in the corner of the factory for a long time.
4to meet up with someone; to hang out
今夜は友達と遊ぶ約束がある。
I have plans to hang out with friends tonight.
学生の頃はよくクラスメートと放課後に遊んだ。
When I was a student I often hung out with classmates after school.
たまには昔の同僚と遊ぶのもいいものだ。
It's nice to hang out with old coworkers once in a while.
5to give oneself up to (gambling, drinking, etc.); to become addicted or consumed by something
彼は仕事も家庭も放り出して博打に遊んでしまった。
He abandoned work and family and became addicted to gambling.
彼はついに酒に遊び、身を持ち崩してしまった。
He finally gave himself up to drink and ruined his life.
6to go to (somewhere) for pleasure or to visit (as in 〜に遊ぶ)
来週、祖父母の家に遊びに行く予定です。
I'm planning to visit my grandparents next week.
休暇に京都に遊びに行った。
I went to Kyoto for fun on vacation.
7to tease or toy with someone (to play with someone's feelings); to toy with
彼は彼女の気持ちを遊んでしまった。
He toyed with her feelings.
子どもたちが友達をからかって遊んでいる。
The children are teasing one of their friends.
8baseball: to throw a pitch in a way that intentionally disrupts the batter's concentration or timing
試合でピッチャーが打者を遊んで三振を取った。
In the game the pitcher toyed with the batter and struck him out.