(SEXUALLY ACTIVE PERIOD) [noun] [U] - the period of the year during which particular animals, esp. the male deer, sheep, etc. are sexually activeDuring the rut, the stags can be seen fighting for females.When the male deer is in rut (= sexually excited) it may fight its rivals for the female.
RUT
Meaning of RUT in English
Cambridge English vocab. Кембриджский английский словарь. 2012