pro ‧ ges ‧ ter ‧ one /prəʊˈdʒestərəʊn $ proʊˈdʒestəroʊn/ BrE AmE noun [uncountable]
[ Date: 1900-2000 ; Origin: pro- + gestation + -one ]
a female sex ↑ hormone which prepares the body for having a baby, and which is also used in ↑ contraceptive drugs ⇨ oestrogen