1. Taru adjective, Adverb taking the 'to' particle

   dense (e.g. fog, dust, etc.); thick

   Usually written using kana alone

   車は砂ぼこりをもうもうとあげて走っていた。

2. vague (as in being unable to think clearly); dim

   Usually written using kana alone

Also written 濛濛【もうもう】moumou、朦朦【もうもう】moumou、朦々【もうもう】moumou