(noun) the amnesia-like phenomenon of not knowing the name of the person currently performing sexual acts on your penis due to (1) dimentia, (2) a general tendency toward slutty behavior or (3) a combination of (1) and (2).
Usage 1: As Gene, who resided in an upscale assisted living facility, entered his 90s, he was unable to recall the names or faces of his visiting children or his sexual partners. As a result, during his frequent sexual conquests just outside the shared dining facility, he would forget the names of the people providing fellatiatic services, or even why they were there. He was suffering from dementia dick.
Usage 2: I invited a guy from a dating app to come to my house. Now he’s riding on my cock but I can’t recall his name. I have dementia dick.
The state of being in which a woman has gotten such good sex from a man that she has contracted short term mental deficiency.
Marcy got dicked down so hard last night that she has dick dementia. She lost her car keys and nearly choked on her own gum.