This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 塟 is uncertain. It visually combines 艹 (grass), 死 (death), and 土 (earth), but the original component relationships are unclear.
The kanji shows grass 艹 over death 死 over earth 土, suggesting burial or covering a dead body with earth and grass. This may hint at a meaning related to burial, but no confirmed meaning is available.
For ソウ, imagine a solemn burial scene: the sound of a slow, mournful 'sou' (ソウ) as the body is laid to rest under the grass and earth.