ukrštati

1. (ukrštati se, of roads, lines) to intersect; to cross
   Na ovom mestu se ukrštaju dve glavne ulice. — Two main streets intersect at this spot.
   U Beogradu se ukrštaju mnogi putevi. — Many routes cross in Belgrade.
2. to cross
   Mačevaoci ukrštaju mačeve na početku meča. — The fencers cross swords at the start of the bout.
   Na sastancima često ukrštaju mišljenja. — They often exchange opposing views at meetings.
3. (of plants, animals) to crossbreed; to hybridize
   Voćari ukrštaju različite sorte jabuka. — Fruit growers crossbreed different apple varieties.

The perfective is ukrstiti; the same root gives ukrštenica "crossword".