nagađati

1. to guess; to speculate
   Ne znam tačno, samo nagađam. — I don't know for sure, I'm just guessing.
   Mediji nagađaju ko će biti novi ministar. — The media are speculating about who the new minister will be.
2. (nagađati se) to haggle; to bargain
   Dugo su se nagađali oko cene stana. — They haggled over the price of the flat for a long time.

Usually used with o + locative (nagađati o uzrocima) or a clause; impersonal nagađa se da… means 'it is speculated that…'.