'Momentously' definitions:

Definition of 'momentously'

From: WordNet
adverb
In a momentous way

Definition of 'Momentously'

From: GCIDE
  • Momentous \Mo*men"tous\, a. [Cf. L. momentosus rapid, momentary.] Of moment or consequence; very important; weighty; as, a momentous decision; momentous affairs. -- {Mo*men"tous*ly}, adv. -- {Mo*men"tous*ness}, n. [1913 Webster]