doubtlessly
2 synonyms for doubtlessly, grouped by meaning and by how common each one is.
Adv — Certainly, with no doubt at all.
Synonyms
Less common
Still standard English, but they carry more weight.
Rare, literary or technical
Precise, but they will stand out — check the sense before using one.
Etymology
From Middle English doutelesly, dowtelesly, equivalent to doubtless + -ly.
Full origin of doubtlessly →