돼먹다 and 헛 먹다 meaning
What does 돼먹다 and 헛 먹다 mean ??
And can someone tell me please how to say " you're really something (else)" in korean ^^

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Answer

돼먹다 & 헛 먹다 both are abuse espretion. Where did u hear it? 
(막)돼 먹다. Randomly became something.  
: 못돼먹어서 성질이 아주 나쁘다
(나이를)헛 먹다. Uselessly spend time. Nothing learned from past time. 
: 이런 것도 못하다니, 나 정말 나이를 헛먹었나봐

U r really something. 너 정말 대단하다
                              넌 정말 뭔가 있다.

Answer

돼먹다 is a vulgar expression of "되다"
It means "become, get to be, be"

(나이를) 헛먹다 means "grow old vainly"

you're really something (else)
너는 정말로 대단하다.