The aftermath of Implied Fellatio or After Fellatio, when the Fellatio act has almost certainly occurred, yet has never been directly spotted. This is usually due to Out-Of-Frame Censoring, or a character Facing Away from the viewer until it's too late to be sure what actually happened, in spite of a few obvious hints.
Most often there is only one partner left alone and/or who's still carrying the last remaining visual cues (Ex: Disheveled, Sunken Cheeks, unconvincingly acting like nothing happened, the presence of Saliva On Penis/Stray Pubic Hair around the mouth, etc.)
It's often used with Cum In Mouth although this alone could simply indicate a Facial without any penetration.