The term IN HEAT can be summarized by two crossword solutions: estrous (7 letters) and irately (7 letters). Estrous is a term used to describe the period of sexual receptivity and fertility in female mammals, including humans. During this period, the female will display certain behaviors that indicate her readiness to mate. Irately is an adverb that describes a feeling of anger or annoyance. It is often used to describe someone who is reacting to a situation with strong emotion.