n. the quality of being beyond question or dispute or doubt; indubitableness.
a. [ L. indubitabilis: cf. F. indubitable. See In- not, and Dubitable. ] Not dubitable or doubtful; too evident to admit of doubt; unquestionable; evident; apparently certain;
n. The state or quality of being indubitable. [ 1913 Webster ]
adv. Undoubtedly; unquestionably; in a manner to remove all doubt. [ 1913 Webster ]
Oracles indubitably clear and infallibly certain. Barrow. [ 1913 Webster ]