Definitions of rut:

noun: a settled and monotonous routine that is hard to escape
Example: "They fell into a conversational rut"
noun: a groove or furrow (especially one in soft earth caused by wheels)
noun: applies to nonhuman mammals: a state or period of heightened sexual arousal and activity
verb: be in a state of sexual excitement; of male mammals
verb: hollow out in the form of a furrow or groove