Definition of a (or one) hundred percent in US English:

a (or one) hundred percent

phrase

  • 1Entirely; completely.

    ‘I'm one hundred percent sure’
    • ‘It has its advantages, but I don't think it's a hundred per cent a good thing.’
    • ‘Addressing a packed press conference he said: ‘I am one hundred per cent responsible for this loss.’’
    absolutely, completely, totally, fully, wholly
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    1. 1.1informal usually with negative Completely fit and healthy.
      ‘I wasn't exactly one hundred percent’
    2. 1.2informal Maximum effort and commitment.
      ‘he always gave one hundred percent for the team’
      • ‘However for the last 3-4 years it seems that giving a hundred per cent is an occasional bonus.’