ad·ver·bi·al /ædˈvɝbiəl/
  (a.)副詞的
  Ad·ver·bi·al a.  Of or pertaining to an adverb; of the nature of an adverb; as, an adverbial phrase or form.
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  adverbial
       adj : of or relating to or functioning as an adverb; "adverbial
             syntax"
       n : a word or group of words function as an adverb