expression, godan verb (-ku)
go into heat; rut
Used for animals, especially cats and dogs, when they enter their mating period. The expression is somewhat colloquial and can be used humorously for people.
うちの猫が盛りがついて、夜中にうるさい。
Our cat has gone into heat and is noisy in the middle of the night.
春になると、野良猫
When spring comes, stray cats go into heat.