This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
雺 combines 雨 (rain) with 矛 (halberd), but the exact historical development is uncertain. It may have originally represented a weather phenomenon like mist or fog, but the connection to 矛 is unclear.
With 雨 (rain) above and 矛 (halberd) below, imagine a mist so thick that a halberd thrust into it disappears—a fog of war. This helps recall the kanji's association with mist or fog.
For ム, imagine a cow mooing in the thick fog: moo -> ム, and the sound is muffled by the mist.