adjective
- that cannot be doubted; patently evident or certain; unquestionable.
adverb
- without doubt; certainly
adjective
- incapable of being doubted; unquestionable
late 15c., from indubitable + -ly (2).
mid-15c., from Latin indubitabilis “that cannot be doubted,” from in- “not, opposite of” (see in- (1)) + dubitabilis “doubtful,” from dubitare “hesitate, doubt” (see doubt).