preficize 

verb
To add an incorrect prefix to a word to make a new word that is understandable, even though it is not necessarily a real word.

see sufficize

"un-" (opposite of, contrary to) + "fast" (characterized by quick motion, operation, or effect) = "unfast" (not a real word, but preficized so you know it means slow)

preficize by FunkRenegade April 22, 2006

perficient 

The opposite of proficient; being totally inept or unskilled at a given job or task.

He is completely perficient at his job and will probably get fired.

perficient by yellacommon October 9, 2020

proficiency 

A high degree or skill

I have a proficiency in painting

proficiency by Lougain Ismail November 2, 2017

proficient

Skilled, adept, competent.

He was very proficient in his task.

proficient by Larstait November 15, 2003

proficiency problem

synonym of skill issue

"this game is dogshit"

sounds like a proficiency problem to me

proficiency problem by hudzell September 7, 2021

certificate of proficiency 

A worthless piece of paper given to an underachiever (or someone over 30 years old with at least one divorce under their belt) from the highly prestigious Community College arena . This piece of paper proudly demonstrates the receiver’s lack of brains and discipline to go to an actual College and receive an actual degree. See also, Participation Award.

“I got my Certificate of Proficiency in Mechatronics Operations in the mail finally!”
Friend: “And you’re proud of that, wow.”

certificate of proficiency by rrrrrrrrrfgrrrrgfdgdfgdfgdfgFF January 26, 2020

Preminized 

To have a preminition about something.

The act of having a preminition

I preminized you died in my dream last night.

Preminized by Tokin' Gay Dude June 14, 2010