Too apparent to be doubted; unquestionable.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "indubitable" in a sentence
"There must have been certain indubitable evidences by which a communication from heaven could be distinguished."
"The unity of the spirit thus becomes and is known as indubitable fact, or rather (I must repeat) not as fact, as if it were or were anything before being known, but as something which is ever more and more coming to be, in the measure in which it is coming to be known -- known to itself."
"But we can distinguish strong rhetoric (for example, "indubitable" arguments that "hard evidence should count") from the obviously dubious or just plain silly."