maslo

1. colloq. (of someone's doing) someone's doing; someone's handiwork
   Ovo je sigurno tvoje maslo, priznaj! — This is surely your doing, admit it!
   Čije je maslo ta glupa šala? — Whose idea was that stupid prank?
2. clarified butter; ghee
   Baka je uvek pržila jaja na maslu. — Grandma always fried eggs in clarified butter.

The figurative sense is usually used with a possessive or genitive: njegovo maslo, maslo tvoje sestre.