What is this character used for: 夰
Most people probably wouldn't know (or have even ever seen) the character 夰, before, but anyway.

汉语大词典


  hào
  
  1 同“昊”。天。
  
  北周  卫元嵩 《元包经·太阴》
  
  雲浮于夰。
  
  李江 注
  
  夰, 天。 
  
  按, 《广韵·上晧》
  
  夰, 《説文》：‘放也。’昊天字從此。 
  
  2 气。
  
  北周  卫元嵩 《元包经·太阴》
  
  夰入于囦, 回浮于元。 
  
  苏渊明 传
  
  夰入于囦, 天氣降也。
  
  李江 注
  
  夰, 氣。


So, for #1 夰 means the same as 昊 - namely "sky/heavens" &amp; #2 gas/air