• 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

Related words...