Doubtlessly

adv

adv ·Uncommon ·Advanced level

Definitions

Adverb

1
Without question; indubitably. proscribed, sometimes
"There are doubtlessly more insects than mammals."
2
Without feeling doubt, without misgivings. obsolete
"Some powers diuine, or els infernall, mixt Their angry ſeedes at his conception: For he was neuer ſprong of humaine race, Since with the ſpirit of his fearefull pride, He dares so doubtleſly reſolue of rule."

Adverb

1
without doubt; certainly wordnet

Synonyms

absolutely admittedly beyond doubt beyond question by all odds certainly

Example

"There are doubtlessly more insects than mammals."

Etymology

From Middle English doutelesly, dowtelesly, equivalent to doubtless + -ly.

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.