1.(of food, especially bread and cake) no longer fresh and therefore unpleasant to eat
eg. He had a stale cake this morning.
2. (of air, smoke, etc.) Stale air or a stale smells is unpleasant because it is no longer fresh.
eg. I can’t stand the stale cigarette smoke.
3.something that is stale has been said or done too many times before and is no longer interesting or exciting。
eg. His always likes telling stale jokes.
4.If you feel stale, you are bored because you have no new ideas or enthusiasm for what you are doing.
eg. Jimmy felt stale after years of work at the same office.