rastopiti

1. to melt
   Rastopi puter u šerpi na tihoj vatri. — Melt the butter in a pan over low heat.
   Sneg se rastopio za dva dana. — The snow melted in two days.
2. (in a liquid) to dissolve
   Rastopi kašiku šećera u toploj vodi. — Dissolve a spoonful of sugar in warm water.
   Tableta se brzo rastopila u čaši. — The tablet quickly dissolved in the glass.
3. (rastopiti se, of feelings) to melt
   Rastopila sam se kad mi je doneo cveće. — I melted when he brought me flowers.

Without se it means to melt something, with se to melt by itself; the imperfective is rastapati.