“Zerg Rush is an online gaming term used to describe an overwhelming scale of attack carried out by one player against another in real time strategy (RTS) games. The term originates from the popular RTS game Starcraft, in which the “Zerg” race is notoriously known for its ability to mass-produce offensive units within a short time frame, thus allowing the player to overpower the opponent by sheer number.”
But go on, type it in anyway, you’ll like it. AFAIK, you can do no harm typing a search term into Google. This is just a one of their little jokes. Har De Har.