what's-her-namenoun [ S ]
informal mainly UK whatsername , US whatshername uk/ˈwɒts.ə.neɪm/us/ˈwɑːts.ɚ.neɪm/also what's-her-faceused for referring to a woman or girl when you cannot remember or do not know her name:
I gave the report to what's-her-name - the new marketing assistant.