beyond a doubt is an adverb meaning "in a manner or to a degree that could not be doubted". It carries one recorded sense.
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”
Definitions, synonyms and semantic relations for beyond a doubt come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.