Definition of doubtlessly in US English:

doubtlessly

adverb

  • 1Certainly; without doubt.

    ‘the man's reputation doubtlessly preceded him’
    ‘he is doubtlessly guilty’
    1. 1.1 Presumably or very probably.
      ‘you've doubtlessly heard me ramble on about the importance of culture’
      ‘we doubtlessly have names in the wrong order’

Pronunciation

doubtlessly

/ˈdoutləslē//ˈdaʊtləsli/