headconvo 

A conversation simulated in your head. Usually never happens in real life, is had for hypothetical purposes.

Headconvos present the opportunity for you to decide someone else's responses.

Guy #1: So what time do you want picking up tomorrow?
Guy #2: What for, are we going somewhere?
Guy #1: Yeah to th- wait, I asked you about it in a headconvo. Uh... You wanna go to the game tomorrow?
Guy #2: Um... Sure...?

headconvo by Nottel Inyu April 25, 2010

headcanon

Used by followers of various media of entertainment, such as television shows, movies, books, etc. to note a particular belief which has not been used in the universe of whatever program or story they follow, but seems to make sense to that particular individual, and as such is adopted as a sort of "personal canon". Headcanon may be upgraded to canon if it is incorporated into the program or story's universe.

In my headcanon, John and Mary bicker like siblings when they're around each other... They just seem like they're brother and sister to me!

headcanon by the-deudliest-firearm July 17, 2012

Headcannon 

A personal belief or interpretation about a story or pice of media that has not been confirmed nor denied in the media itself.

It’s my headcannon that they eventually make it back home, but we’ll never know because the series ended with them attempting to escape.

Headcannon by Hellohihey February 9, 2020

Headcanon

(also written as "head canon," but it's really one word.)

An idea, belief, or aspect of a story that is not mentioned in the media itself, but is accepted by either the media consumer themselves or the fandom in general. If it is confirmed by the creator of the story, it becomes canon.

In Homestuck , a popular webcomic , many suspect the headcanon that the trolls are carnivores, because of their natural homicidal tendencies and sharp teeth. It's never explicitly stated in the comic that this is true, but it'd be kind of dumb to assume they're a race known for salads and ice cream sundaes.

Headcanon by TickTockTimeTraveler October 12, 2014

Headcanon

Now... reality can be whatever I want...
-Thanos

person 1: omg i headcanon todoroki and dek-
person 2: please stfu

Headcanon by ._.daydreaming April 11, 2022

Headcanon

The non-canon personal ideas, opinions and believes that certain person or group of people feels strongly attached to, about a certain work of fiction (book, movie, cartoon, anime series, manga, comic book, etc...)

Sometimes people put their own headcanons above the actual canon of what was actually shown.

Person A: Android 17 is barely SSJ3 level, and that is exaggerating! Goku in SSJ Blue could have defeated 17 with a single punch!

Person B: That is your Headcanon. If he is a SSJ3 level character, then why Goku fought 17 with SSJ Blue instead of SSJ3, like he did with Trunks in a previous arck? Also, how can a SSJ3 level character resist attacks capable of hurting SSJ Blue evolution Vegeta and SSJ Blue kaioken x20 Goku that are 20 times more powerful than a SSJ Blue, 17 received a kick from Jiren, meant for Vegeta Blue Evolution in episode 127, and also took an explotion from Jiren that was able to knock out Goku and Vegeta, and he was still able to fight, a SSJ3 level character shouldn't be able to do that!

Headcanon by TruthTellerX01 July 10, 2019

headcannon 

A miniature cannon mounted on one’s head. Used mainly to prank unsuspecting friends. A headcannon is very difficult to ignore.

“I’ve got a new headcannon.”
“Yeah?”
“Yeah.”
*launches cannonball at friend*

headcannon by coyotedomino March 2, 2018