opozicija

1. (in politics) opposition
   Opozicija je najavila proteste za subotu. — The opposition has announced protests for Saturday.
   Posle izbora stranka je prešla u opoziciju. — After the election, the party went into opposition.
2. opposition; resistance; contrast
   Njegov predlog naišao je na jaku opoziciju u firmi. — His proposal met with strong opposition at the company.

It is mostly used in the political sense; «biti u opoziciji» means to be in opposition.