You’ve probably experienced this: You wake up in the morning, grab a glass of water that you intentionally or unintentionally left out overnight, and take a big swig of that room-temperature water. Your immediate reaction is, “That’s stale water!”
And while “stale” may not be the ideal descriptor, you’re not wrong. It has an unmistakably stale taste as it goes down and may also leave a bad taste in your mouth.