MERQ is an acronym that stands for Make 'Em Rage Quit. It's very similar to the verb, merk, which means to beat someone, kill someone, insulting someone, or injuring someone. But in this context, you're making them "rage quit" instead.
Bro! I'm beating this kid 6-0 on FIFA! -guy leaves- HA! I made 'em rage quit! MERQ'd. Lawlzlawlzlawlz