opovrgnuti

1. to refute; to disprove; to deny
   Naučnici su opovrgli tu staru teoriju. — Scientists disproved that old theory.
   Ministarstvo je odmah opovrglo pisanje novina. — The ministry immediately denied the newspaper reports.

The imperfective counterpart is opovrgavati; past forms are opovrgao, opovrgla.