Phrase originating in Britain that is uttered by ravers/binge-drinkers when they are. Usually shouted repeatedly whilst loud electronica/techno/dance/rave music is blaring, and whilst the speaker is raving/dancing
"LET'S GO FUCKING MENTAL
, LET'S GO FUCKING MENTAL, LET'S GO FUCKING MENTAAAAAAL!!!"
*smashes glass over own head rendering himself unconscious*