(Onomatopoeic) to become soft and limp or supple, as when vegetables are cooked; often used as “しんなりする”.
玉ねぎを弱火で炒めるとしんなりして甘みが出てくる。
If you sauté onions over low heat, they become soft and release sweetness.
サラダは時間が経つとドレッシングでしんなりしてしまう。
Salad wilts from the dressing after a while.
花瓶の花が暑さでしんなりしてきたので水を替えた。
The flowers in the vase started to wilt from the heat, so I changed the water.