ラグい ragui

ラグい takes the English lag and turns it into a Japanese adjective by adding い. That machine is one of the most productive in modern Japanese: ナウい from now in the disco decades, エモい from emotional a generation later, キモい from a native word by the same trimming logic. If a concept matters enough, it eventually grows an い.

The result behaves like any adjective, so you can say ラグかった for the match you lost last night. And you will, because ラグい is the first explanation offered for every defeat in an online game. Occasionally it is even the true one, which is precisely what keeps the excuse alive.