When you receive an email and compose a reply in your head but don't actually type and send it.
Deepa: Why didn't you respond to my email?
Eric: I did--you didn't get it?
Deepa: No. When did you send it?
Eric: (checking sent items) Oh, I guess I never did. It must have been a mental reply.
by Jim Kudrik November 8, 2008
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Girls who reply to popular videos on Youtube just to get views.

They usually have their boobs hanging on the thumbnail to catch viewers then make a short video explaining stuff you already know. Also can be called the spam on youtube.
Random kid. "Oh I just watched nighahiga's newest video!"
*sees a reply video that has a girl with a huge rack as thumbnail*
" I wanna watch that"
30 seconds later...
"That was f**king dumb as f**k! I hate these reply girls!"
by hater of trolls February 28, 2012
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Clinical term for message board blue balls, specifically when someone starts a thread and that thread is locked for whatever reason, before you can follow up with a brilliant reply and/or the joke's punchline.
Eeth's thread failure gave me horrible reply-vasocongestion pains...I spent 15 mintues photoshopping an image for him but his crappy thread got locked before I could post it.
by Seb-X April 4, 2008
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1: Really annoying females on YouTube who reply to any mainstream trailers, news, viral videos or any videos that attract a lot of attention. They are a new type of attention whore.
2: the real life jackoffasaur
Daddy: Son, I we need to have a chat. Have a seat over there and make yourself comfortable.
Billy: Okay, Dad.
Daddy: Son, there are people in this world who resemble that of a jackoffasaur. These annoying creatures are known as "Reply girls."
Billy: Why are you telling me about this, Daddy?
Daddy: So that you can defend yourself when you confront one on YouTube.
Billy: OH! Can I burn it?
Daddy: Why, yes, you can, Billy. Yes, you can.
by masterBETA February 25, 2012
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When one has a tendency to read a message yet not able to reply to it.
"Hey Sally, did James get back to you about Sunday?"
"Nah, he's being a no reply bitch"
by Sxcbadbois August 9, 2015
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RBNR is used in a chatzone where someone reads a message and doesn't reply.
Here's an example of someone Reading But Not Replying in a chat;

19:01 Dan: Hello? (READ 19:02)
19:03 Dan: I know your there:L (READ 19:03)
19:04 Dan: rbnr? (UNREAD)
by SamMorganOnline August 5, 2012
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When you accidentally call every member of a large group chat on Microsoft Teams instead of the single person you tried to call.
Jennae was so embarrassed that she reply-called the entire team.
by Patton Freakin' Oswalt September 2, 2021
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