The term for a timeframe during a human female's monthly cycle in which she is fertile or receptive for impregnation. Often accompanied by outward physical/pheromonal indicators. Human females have created pseudo estrus indicators which now inaccurately reflect femininity (high heels which thrust out the buttocks, lipstick and rouge which falsely indicate a greater blood flow caused by excitement, and undergarments which create an illusion of plenty), surgery to create an illusion of youth.