When people are too casual for the situation that they're in. References the highly competitive sport of Super Smash Bros. Melee
Jon: Hey Billy, you failed your math exam!
Billy: Whatever -__-
Jon: Stop being such a Melee Casual!
Casual leisure is an immediately, intrinsically rewarding, relatively short-lived, pleasurable core activity, requiring little or no special training to enjoy it. It is fundamentally hedonic, pursued for its significant level of pure enjoyment, or pleasure. The termed was coined by Robert A. Stebbins (1982) in a conceptual statement about serious leisure, which depicted its casual counterpart as all activity not classifiable as serious. As a scientific concept casual leisure languished in this residual status, until Rojek (1997) and Stebbins (1997; 2001) belatedly recognized its centrality in leisure studies. Stebbins sought to elaborate the idea as a sensitizing concept for exploratory research, as he had earlier for the idea of serious leisure.
In broad, colloquial language casual leisure, hedonic as it is, could serve as the scientific term for doing what comes naturally. Yet, despite the seemingly trivial nature of most casual leisure, I argue elsewhere that it is nonetheless important in personal and social life (Stebbins, 2001b).
A braggy sort of accomplishment in the game Rainbow Six Seige where you are to go into a casual game and one round kill all five people.
Man, I just got a Casual ace on those noobs.