Definition of pro-oestrus in English:
pro-oestrus
(US pro-estrus)
noun prəʊˈɛstrəsprəʊˈiːstrəs
Biology The phase of the reproductive cycle in female mammals immediately preceding oestrus, characterized by the growth of ovarian follicles and development of the endometrium.
Origin
Early 20th century; earliest use found in Proceedings of the Royal Society of London. From pro- + oestrus.