1Being on very close, friendly terms with someone; also refers to such a close friend. Common in children's speech, but also used for close adult friendships.
私と彼女は幼稚園からの仲良しです。
She and I have been close friends since kindergarten.
隣の家の犬とうちの犬は仲良しで、いつも一緒に遊んでいる。
The neighbor's dog and ours get along great and always play together.
あの二人は喧嘩ばかりしているけど、実は仲良しなんだよ。
Those two are always fighting, but they're actually really close friends.
職場に仲良しの同僚がいると、毎日が楽しくなる。
Having a close friend among your coworkers makes every day more enjoyable.
2A euphemistic, gentler way of referring to having sex — used either indirectly among adults or in child-friendly explanations. Colloquial.
子どもに「赤ちゃんはどうやってできるの?」と聞かれて、「パパとママが仲良しするとできるんだよ」と説明した。
When my child asked, "How are babies made?" I explained, "They come from mommy and daddy being intimate."
あの二人、最近やけに距離が近いと思ったら、もう仲良ししてるって噂だよ。
I thought those two had been getting oddly close lately — turns out there's a rumor they're already sleeping together.