The title above has two meanings, but only one of them is universally accepted. Which are you thinking of?
From Merriam-Webster (American):
1: for a moment (was momentarily delayed)
archaic : instantly
3: at any moment : in a moment (will be leaving momentarily)
I make one new blog post every weekday: each day of the Western business week running Monday to Friday. One moment of each day, I post a new entry to this page.
If I updated according to the uncontroversial usage for momentarily, you wouldn’t see any of them for long: they’d be online for just that one moment, and no longer!
Of course, you probably thought from the title that I would be making a new post very soon. The question is, did you think I had made a grammatical error?
A Questionable Coinage for an Established Word
You can see that Merriam-Webster does not; the “incorrect” usage of momentarily to mean “almost immediately” is present and accounted for. But just as prescriptivists and descriptivists have been sparring over hopefully for four decades, people can get crabby about the proper use of momentarily.
The prescriptivists are sick of the word being shoehorned into waiting rooms and voicemail queues:
The doctor will be with you momentarily.
Your call will be answered momentarily.
You will receive a grammatically incorrect response momentarily.
The descriptivists, on the other hand, see speakers creating a practical new definition that ends a sentence more conveniently than the three-word “in a moment” and more precisely than the hazy “shortly.” While we may not be able to measure the length of a moment, it is at least a countable noun: we know that “a few moments” would be longer than just one.
But Should You Use It?
This abbreviation of “in a moment” is here to stay, at least in the United States. What M-W cites as the third definition for momentarily, Princeton’s WordNet cites as the first. The usage would not pop up in so many places if it did not fulfill a lexical need. Be careful, though: I don’t think the need for momentarily has permeated the entire English-speaking population to the level that you can use it with the impunity afforded to a word like hopefully, a formerly controversial usage that takes the place of the mouthful “it is to be hoped.” The British seem particularly irked by the iffy use of momentarily, so watch out if you’re submitting something to the Financial Times.
In any case, this all means that my pragmatic prescriptivism still gets activated when a writer I’m editing promises to prove her point “momentarily” in a paper.
It also means that I make use of hopefully all the time–but that’s a post for another moment.