1. Become suddenly very angry
   "The professor went off the deep end when the student didn't know the answer to a very elementary question";
   - flip one's lid [N. Amer, informal], blow up [informal], throw a fit [informal], hit the roof [informal], hit the ceiling [informal], have a fit [informal], blow one's stack [N. Amer, informal], fly off the handle [informal], flip one's wig [US, informal], lose one's temper, blow a fuse [informal], go ballistic [informal], go mental [informal], blow a gasket [informal], go ape [informal], blow one's top [informal]
    
2. Behave erratically or irrationally
   "He went off the deep end when he heard the news of his job loss"

Derived forms: goes off the deep end, went off the deep end, going off the deep end

Type of: rage