Noun
surrogate mother (plural surrogate mothers)
A woman who gives birth to a child not her own, with the intent to give that child up to at least one of the biological parents once it is born.
Synonym: (informal) surro
My mother, father, stepmother and surrogate mother have all died of cancer; my best friend has got terminal cancer and at least five of my other friends have had cancer but survived it. Arabella Weir