If the pilot announces, “we will be in the air momentarily,” it means you’re going to crash.
If the waiter assures you, “your food will be here momentarily,” it means you’d better eat fast.
If you are told “a customer service representative will be with you momentarily,” it means she won’t have much time to assist you.
If the theater manager says “doors will open momentarily,” you’d better hope you’re at the front of the line.
“Momentarily” means “for a moment” or “briefly,” not “in a moment” or “soon.” You may disagree, lots of people do—usually the ones who use it incorrectly or who quote a source that has just plain given up and added the erroneous definition.
I won’t be surprised by comments that cite sources accepting “in a moment” as an acceptable definition. It happens all the time. I once lost a bet with someone when I claimed “irregardless” wasn’t a word and that it couldn’t be found in the dictionary. I placed my bet, looked it up and there it was: “irregardless: an incorrect use of regardless.” As with “sherbert,” some sources have just shrugged their shoulders and looked the other way.
But I am fair and have an open mind. If you do disagree with me, feel free to state your case. I will listen to you momentarily.