otopiti

1. (+ acc.) to melt; to thaw
   Sunce je brzo otopilo sneg na krovovima. — The sun quickly melted the snow on the roofs.
   Otopi čokoladu na pari pa dodaj puter. — Melt the chocolate over steam, then add the butter.
2. (otopiti se) to melt; to thaw
   Sladoled mi se otopio dok sam stigao kući. — My ice cream melted by the time I got home.
3. (in a liquid) to dissolve
   Otopi kašičicu soli u čaši tople vode. — Dissolve a teaspoon of salt in a glass of warm water.
4. (of feelings, relations) to melt; to soften
   Njen osmeh mu je otopio srce. — Her smile melted his heart.
   Posle razgovora led između njih se otopio. — After the talk, the ice between them thawed.

Without «se» the verb is transitive (melt something); with «se» it means to melt by itself.