The phrase skill floor refers to the minimum level of skill necessary to do anything useful in a given domain. It's the corollary to a skill ceiling and as such usually comes up in the realm of gaming. Low skill floors mean low barriers to entry which is typically desirable. Players can lose interest before they've made any noticeable progress if they encounter too much of a challenge. At the same time most games require a certain minimum competence to play and only so much can be done to ease the player into a new adventure. Skill floors can also refer to the difficulty of some element of a game. For instance, it's common for one or more playable characters in a fighting game to handle very different from the rest of the characters making them hard to adapt to. Once their quirks are mastered they play just as well as any other but it's a rough start that puts people off from them.
Some examples of high skill floors can be found in Dwarf Fortress, Super Hexagon, and I wanna be the Guy. In the base game, Dwarf Fortress's art is ASCII and the interface is a startling array of hot keys so players tend to bounce off it in only a few minutes. People who push through find it extremely quick and intuitive. Super Hexagon levels last a hand full of seconds during the first hours of play. This later results in a zen like play experience that's hard to replicate. I wanna be the Guy's whole selling point is that it's super hard. Good luck getting past the first two screens. Each of these has a good (or at least thought out) reason why the game has such a high skill floor and none of them will ever be mainstream as a consequence.
Skill floors use to be a much more common during earlier eras. They've been abrogated by tutorial levels which can lay out the games mechanics in a sequential, piecemeal fashion but carry their own risks with boring the player with annoying busy work. As it stands, skill floors are rarely encountered but when they are they can be a significant impediment to a game's viability.
IRON NODER THE THIRTEENTH