What’s his/her face
Definition 1 of 1
Pro Tip 1/3Casual Speech
Used in informal conversation, often among friends or peers. 
At the party, I bumped into what's her face from our history class.
Pro Tip 2/3Avoid in Formality
Not suitable for formal contexts such as business or academic discussions. 
In the meeting, I didn't say 'what's his face,' I used the person's actual name.
Pro Tip 3/3Potentially Dismissive
Can imply indifference or slight disrespect towards the person being referred to. 
She was upset when he referred to her as 'what’s her face'.