From Longman Dictionary of Contemporary Englishfoundlingfound‧ling /ˈfaʊndlɪŋ/ noun [countable] old use SSCa baby who has been left by its parents, and is found and looked after by other people
Examples from the Corpus
foundling• Maria della Scala in Siena as a foundling.• They provided hospices for the sick or for raising the innumerable foundlings.• Of about half a million foundlings christened in workhouses after 1728, only 40 percent survived to their second birthday.• Miriam and Amina were not foundlings.• Our foundling is fast becoming a woman. 