beyond a shadow of a doubt

Từ điển WordNet v3.1 - WordNet Dictionary

adverb

in a manner or to a degree that could not be doubted
- it was immediately and indubitably apparent that I had interrupted a scene of lovers
- his guilt was established beyond a shadow of a doubt
• Syn:
indubitably, beyond doubt, beyond a doubt
• Derived from adjective:
indubitable (for: indubitably)