phrase (of particular male animals) sexually excited: （雄性动物）发情 The bull elephant seal only puts on this display when in rut. We spied two bull moose in rut, battling among the trees. Avoid approaching deer during this season, as they can be aggressive when they are in rut. Bucks tend to eat less when in rut. The walruses exhibit a slightly different behaviour when in rut. See also