verb/fɔ̃.dʁə kɔm nɛ.ʒ‿o sɔ.lɛj/
to shrink at a rate of knots, to melt away (to dwindle or diminish very rapidly)
“Mes économies fondent comme neige au soleil.” — My savings are melting away.
Literally, “to melt away like snow in the sun”. Compare Dutch als sneeuw voor de zon verdwijnen.