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