naglavačke

1. headfirst; headlong
   Skočio je naglavačke u bazen. — He dived headfirst into the pool.
   Pao je naglavačke niz stepenice. — He fell headlong down the stairs.
2. upside down
   Posle žurke stan je bio okrenut naglavačke. — After the party the flat was turned upside down.
   Beba nam je okrenula život naglavačke. — The baby turned our life upside down.

Often used in the phrase “okrenuti naglavačke”.