go off the deep end

go off the deep end and jump off the deep end 

1. Lit. to jump into a swimming pool where the water is over one's head and one needs to be able to swim You are still only learning to swim. Are you ready to go off the deep end? He jumped off the deep end where he would make a bigger splash.

2. Fig. to become deeply involved (with someone or something) before one is ready. (Applies especially to falling in love.) Look at the way Bill is looking at Sally. I think he's about to go off the deep end.

3. Fig. to act irrationally, following one's emotions or fantasies. Now, John, I know you really want to go to Australia, but don't go jumping off the deep end. It isn't all perfect there.

See also: deep, end

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go off the deep end  (informal)

to suddenly become very angry or upset and start shouting at someone One minute we were having a perfectly reasonable discussion and the next minute you just went off the deep end!

See also: deep, end

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go off the deep end

to become so angry or upset that you cannot control your emotions Tom will go off the deep end if Jerry can't pay him the money he owes.

See also: deep, end