1N-COUNT [usually singular, usu in aN](人、生活或工作)刻板乏味,一成不变,老一套 If you say that someone is in a rut, you disapprove of the fact that they have become fixed in their way of thinking and doing things, and find it difficult to change. You can also say that someone's life or career is in a rut. (人、生活或工作)刻板乏味,一成不变,老一套 [disapproval]
I don't like being in a rut — I like to keep moving on.
3N-SING [usually theNOUN, also inN](动物的)发情期The rut is the period of the year when some animals such as deer are sexually active, and the males fight each other to mate with the females. (动物的)发情期