Real Dictionary

wet nurse
a woman hired to suckle another's child
a woman hired to suckle another's infant
to act as a wet nurse to (a child)
to act as wet nurse to
countable noun: In former times, a wet nurse was a woman who was paid to breast-feed another woman's baby.
noun: a woman hired to suckle the child of another

wet-nurse in American English
transitive verb: to act as a wet nurse to (an infant)