This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
妰 combines 女 (woman) with 乍, which may contribute sound. The exact historical development is uncertain.
A woman 女 beside 乍, but the meaning is unclear. Imagine a quiet woman standing still, as the kun reading suggests calmness.
For チャク, imagine a woman wearing a choker necklace: choker -> チャク, and she remains quiet and still.