The world "halfalogue" seems to have been coined in an academic article titled "Overheard Cell-Phone Conversations: When Less Speech Is More Distracting," by Lauren L. Emberson and colleagues. 

In it, Emberson defines a halfalogue as "only half of a conversation." It's the half of a conversation that you hear when someone near you is on their phone.

Which is so annoying, and distracting! In fact, Emberson's study suggests that when people are sitting near a halfalogue, they do worse on tasks requiring attention (compared to when they're sitting near other types of ambient speech, like complete conversations). She reckons that halfalogues are so distracting because they aren't predictable: we're hearing things, but we're missing a chunk of the context or the continuity, and that bugs us.

This term "halfalogue" has entered popular speech, and has even been used figuratively to mean "any kind of correspondence where one side is missing."

Part of speech:

Noun, the countable kind: "My seatmate on the plane kept up a halfalogue until, mercifully, the captain told us to turn off our phones."

Other forms: 

The plural is "halfalogues."

You can spell it "halfalog," if you like.

I haven't found any examples of people using "halfalogue" as a verb, but we did verbify "monologue" and "dialogue," so go for it! "My seatmate halfalogued for twenty minutes. It made me twitchy."

how to use it:

You'll find "halfalogue" in at least one English dictionary. It's a reasonably popular word online and in the academic community, and it's easy to understand.

So feel free to use it in conversation! "I was distracted by a halfalogue." "The waiting room is a bleak place, full of halfalogues and stale coffee."

I can even see us applying the word even more broadly to mean "a conversation or correspondence where only one of the two parties cares, or pays attention." You might prefer to use the word "monologue" for that meaning, though.

examples:

"The Archives of American Art holds a large collection of John Singer Sargent's letters. Most are notes he sent, not ones he received. As scholars, how are we to address the challenge of this partial conversation, or halfalogue?"  
   — Erica E. Hirshler, Archives of American Art, Spring 2019

"#1 [worst thing about my anxiety] is the f******* halfalogue autocomplete... When you listen to half a dialogue or even just pieces when you're in public and your brain fills in the blanks to make it fit the anxiety narrative. Every 'he' obviously means me, laughing is definitely because I'm clattering too loud with the cutlery in the cafeteria."
   — Asocial_Stoner, Reddit.com, 2020

has this page helped you understand "halfalogue"?

Awesome, I'm glad it helped!

Thanks for letting me know!
If you have any questions about this word, please message me at Liesl@HiloTutor.com.

study it:

Explain the meaning of "halfalogue" without saying "one audible side of a discussion" or "a broken half of a conversation."

try it out:

Do halfalogues irritate you? A little? A lot? Not at all? Would you rather be held hostage to a halfalogue for ten minutes, or be bitten by a mosquito? 

I bet that, the more that halfalogues irritate you, the more you care about the narrative flow in a story, or the conversational flow between people. Would you agree or disagree, and why?

If you like, use this space to write. (To save your work, copy and paste it into an email or a document.)

before you review, play:

Try to spend 20 seconds or more on the game below. Don’t skip straight to the review—first, let your working memory empty out.

Our game for January: "Is That a Real Word?"

In each issue, I’ll give you three, um, written phenomena. You decide if each is a real word—and most importantly—why or why not. If someone were to dispute your judgment, how would you defend it? For fun, try comparing your responses with a companion’s. And if you like, you can compare yours with mine, which I’ll list at the bottom of the issue.

Try these today:  Out of "loosey-goosey," "nother," and "turducken," which, if any, are real words?

review this word:

1. A near opposite of HALFALOGUE is

A. PROLOGUE.
B. EPILOGUE.
C. DIALOGUE.

2. Wendy Rose describes _____ as a halfalogue: "______."

A. a conference .. [It] returned Nov. 30, the second virtual installation of the regularly occurring, multi-curated, multi-disciplinary event held in 2020

B. a film .. Delivered in two parts, [it] loads the audience with fragmented details in Part 1, allowing us to build a plotline that twists in the second part, as the missing information is delivered, piece by piece

C. a play .. Written by Trudy Morgan-Cole, [it] showcases every facet of the fascinating Armine Nutting Gosling—a supportive wife, dedicated mother, caring sister and a deeply important woman in the history of Newfoundland's suffragist movement

Answers to the review questions: 1. C 2. B Let's compare notes from the game: I say they're all real words! "Loosey-goosey:" Oh, my. Such a ridiculous term. I don't blame the OED for ignoring it, but it's reared its floppy little head in other dictionaries.  "Nother:" I was almost ready to die on this hill because I really, really dislike this word! But it's got citations in the OED dating back to 1325. "Turducken:" Isn't it ghastly to shove three things into one in this way? (The words or the birds? Yes.) Nevertheless, "turducken" appears in the OED with an initial citation from a 1982 issue of Newsweek.

a final word:

I hope you're enjoying Make Your Point. It's made with love. I'm Liesl Johnson, a reading and writing tutor on a mission to explore, illuminate, and celebrate words. From my blog: On vocabulary...       36 ways to study words.       Why we forget words, & how to remember them.       How to use sophisticated words without being awkward. On writing...       How to improve any sentence.       How to motivate our kids to write.       How to stop procrastinating and start writing.       How to bulk up your writing when you have to meet a word count. From my heart: a profound thanks to the generous patrons, donors, and sponsors that make it possible for me to write these emails. If you'd like to be a patron or a donor, please click here. If you'd like to be a sponsor and include your ad in an issue, please contact me at Liesl@HiloTutor.com. A disclaimer: When I write definitions, I use plain language and stick to the words' common, useful applications. If you're interested in authoritative and multiple definitions of words, I encourage you to check a dictionary. Also, because I'm American, I stick to American English when I share words' meanings, usage, and pronunciations; these elements sometimes vary across world Englishes.