Skill floor- The minimum skill required to play a hero effectively. Lucio for example has a very low skill floor. Even with very little skill he can still be played effectively.
literally googled
edit: also, this is from the link you provided yourself
"This brings us to skill floors. A skill floor is the counterpart to a skill ceiling. A skill ceiling is the level of play that’s possible with training and mastery. A skill floor is a way of describing how difficult it is to begin the process of mastery. For example, playing Widowmaker in Overwatch isn’t easy if you don’t have a background in other FPS titles. In order to even be relevant with her, you need to have exceptional aim and positioning. The skill floor for Widowmaker, in other words, is very high — if you want to be somewhat competent, you need to have mastered a variety of game mechanics."