IPA: /ˈmɛltˌwɔːtə/
KK: /mɛltˌwɔtər/
Water that comes from the melting of snow or ice.
In spring, the meltwater from the mountains flows into the rivers.
Meltwater is formed from "melt" (from Old English *meltan*, meaning to soften or dissolve) and "water" (from Old English *wæter*, meaning liquid that falls as rain or flows in rivers). The term refers to the water produced when ice or snow melts.
Think of ice 'softening' ('melt') and turning into 'liquid' ('water') — that's what meltwater is.