Definition of vastly in US English:

vastly

adverb

  • To a very great extent; immensely.

    ‘business practices differ vastly from country to country’
    as submodifier ‘a bunch of talented and vastly experienced players’
    • ‘Twelve years later, the situation had vastly improved.’
    • ‘Technology vastly increases children's capacity for secrecy and their vulnerability to exploitation.’
    • ‘This instance illustrates the social construction of acceptability, whereby different audiences may respond to the same set of works in vastly different ways.’
    • ‘The 1993 American remake is vastly inferior.’
    • ‘The show included three sculptures replicating unmarked packets of sweetener at vastly larger-than-life size.’

Pronunciation

vastly

/ˈvæs(t)li//ˈvas(t)lē/