margotko,
já z chorvatštiny nepřekládám, ale na netu jsem našla tohle:

Serbo-Croatian

Interjection

u pičku materinu (usually followed by an exclamation point) (Cyrillic spelling у пичку материну)

(idiomatic, vulgar, slang) Expression of terror, awe, surprise, shock, etc.
U pičku materinu, još nikad nisam vidio takav nered! — Holy shit, I""ve never seen such a mess before!
(idiomatic, vulgar, slang) Used as an intensifier.
Tip je retardiran u pičku materinu! — The guy is so fucking retarded!

Usage notes
Commonly used in the following phrasal constructions:

ići u pičku materinu — to enter chaotic, damaged or failed state, to fall apart
Čini se da c(ij)elo društvo ide u pičku materinu! — It appears that the whole society is going to hell!
Idi u pičku materinu! — Go to hell!
slati u pičku materinu — to tell somebody to fuck off
Mrš u pičku materinu pederčino jedna maloumna! - Fuck off you stupid faggot!
goniti se u pičku materinu
nositi se u pičku materinu

Related terms
u tri pičke materine
u pizdu materinu