'Threateningly' definitions:

Definition of 'threateningly'

From: WordNet
adverb
In a menacing manner; "the voice at the other end of the line dropped menacingly" [syn: menacingly, threateningly]

Definition of 'Threateningly'

From: GCIDE
  • Threatening \Threat"en*ing\, a. & n. from Threaten, v. -- {Threat"en*ing*ly}, adv. [1913 Webster]
  • Threatening letters (Law), letters containing threats, especially those designed to extort money, or to obtain other property, by menaces; blackmailing letters. [1913 Webster]