To be boiled or cooked through (intransitive): when food becomes soft or fully cooked by boiling/simmering.
じゃがいもが煮えてきたので、火を弱めてください。
The potatoes are coming to a boil, so please lower the heat.
鍋の中の煮物がよく煮えて、とても味が染みている。
The simmered dish in the pot is well cooked and very flavorful.
魚は煮えるのに時間がかかる部位と早く煮える部位がある。
Some parts of fish take longer to cook than others.
その話は煮え切らない返事で終わった。
The conversation ended with a noncommittal answer. (idiomatic use)