This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 霚 is uncertain. It visually combines 雨 (rain) with 敄, but the component relationship is unclear.
With 雨 on top and a complex lower part, 霚 looks like a weather-related character, but its meaning is unclear. Imagine a mysterious foggy shape that defies easy description.
For ム, picture a cow saying 'moo' in the fog: moo -> ム, and the sound echoes through the misty 霚.