The phrase "an indubitably" is not correct in standard written English.
The word "indubitably" is an adverb and should not be preceded by the article "an."
Example: "The results of the experiment were indubitably conclusive."
Alternatives: "undoubtedly" or "certainly."
Conceive of my astonishment, therefore, when his only reply was a grunt, and an indubitably unpleasant grunt at that.
There are many health and environmental implications of fracking, but flammable tap water appears to be an indubitably serious drawback.
If you reach an indubitably true conclusion, your conjecture may have been true.
Religiously speaking, a physical land simply cannot be holy for Leibowitz: "The idea that a specific country or location has an intrinsic "holiness" is an indubitably idolatrous idea".
The common assumption was that the dialectic syllogism is an indubitably valid deductive scheme, but that probable premises produce only probable conclusions or opinions (Buridan, Quaestiones, 19; Buridan, Summulae, 347).
The outgoing ForTwo, though an indubitably clever piece of packaging, has always been let down by its oafish road manners at anything above walking pace, that head-nod gearbox, stumpy wheelbase and sloppy steering combining to induce seasickness in all but the hardiest travellers.
"I'd be a criminal indubitably, or some manner of sociopath.
Gnutti's Hopa investment group is sanguine with cash after he sold his Telecom Italia stake; a stake indubitably enriched by the acumen of Colaninno, who masterminded the 1999 TI takeover.
One possibility is Jean-Claude Juncker, a centre-right prime minister from Luxembourg, indubitably a small country.
It may not have been the most traditional Arctic meal, but thanks to the determination of a few innovative Icelandic farmers, it was indubitably a local one.
With its fealty to celebrity and golf, the Buick Roadster he was examining under Koh's watchful gaze was indubitably an American thing.
