As I can see everyone throws the word "glitch" whenever they find something relatively out of the ordinary out there. I would like to know though, what is the definition of a glitch according to you?

@Wak017Wak017 For me I think a "glitch" is any time you can use intended mechanics to achieve an unintended result.
So for this game I would call pseudo wave and reverse grapple block a glitch, but not WBJ or the early grapple beam jumps. While the WBJ might not have been intentional, the slide jumps were definitely something they knew about.

Stuff like axis skew, camera lock, and ledge warp are definitely not intended mechanics though.

But who knows maybe it is all unintended and the devs just liked how it effects the runs.

Early bombs does have a unique animation for Kraid so that one is definitely not a glitch.

I don't agree with that definition of glitch @jerryb216jerryb216 . I think about it through the perspective of Melee. If it's something the devs surely knew about or is a quirk of the engine, it's an exploit, not a glitch. So in Melee this would be why wavedashing is generally considered an exploit. You use something the devs knew about like slide jumping in a way they wouldn't have expected, like getting early bombs. Glitches usually are things that aren't supposed to be possible in the first place, even through exploitation of the engine or mechanics. Something like the Axis skew or camera lock are clear examples of that. It's all still pretty subjective though, I just think it's valuable to differentiate exploits from glitches.

@LinkLuver01LinkLuver01 it is pretty subjective, but the early bombs was completely intended as there is a alternate way to quick kill Kraid using a morph ball booster or whatever the tubes are called.

But I agree with your definitions though.

Using any mechanic (intended or not) in a dysfunctional manner, dysfunctional in a code sense, i.e. interrupting a state your character should be locked in, going through a collision that should clearly stop you, etc. Cleverly exploiting mechanics in a way that was unintended isn't necessarily a glitch, as long as you stay in the boundary of how the code should run regarding the game state, your character states/hitboxes, and the environment state/hitboxes.

This question is not easy to answer. It is also the main reason why there is no glitchless category.
For me glitches are tricks to break the (intended) rules of the game.
For example: PseudoWaveBeam.
Let's say a game rule is, that samus can't shoot through walls with standard beam.
The devs implement checks to enforce this rule: All beams are collision checked with the the outside surfaces of world assets. If a collision is detected, the beam is stopped and the explosion animation is triggered.
Speedruners now do slide jumps to force samus into a specific animation that always brings the weapon arm into a specific position, even then when it shouldn't be possible due to world boundaries.
So samus weapon arm goes out of bounds. From inside the wall there is is no collision line that intersects with the beam-path, because collisions are only checked against beam-paths coming from the outside and not from the inside (due to math and performance improvement).
So the in game sanity check that should have enforced the rule "no shooting through walls" was circumvented with tricks.
Thats what I call glitch using.
Some people argue that everything that the game lets you do, is allowed an therefore ok. Which is kind of the whole point of regular any% speedrunning.
But nonetheless the conceptual general rule that "samus can't shoot through walls with standard beam" was violated.
This is only my point of view. Others might see it differently. It is an almost philosophical question.

I like Terbium Definition.

Expanding on that, Water Bomb Jump is also a Glitch.

There's a flag that prevents water bomb jumps outside of floor level.
That flag is circunvented at storing the special setup the WBJ needs.
thus making it a glitch.

TLDR: WBJ was not intended but discovered, hence it is a glitch.

A good example for something that is likely unintended, yet is definitely not a glitch would be infinite bomb-jumping to pass the pressure plate door to obtain Flash Shift.

Thanks for all the answers everyone. I am currently making an explanatory video on what exactly is a glitch. Because the definition is all over the place and people can't seem to get along when it comes to define a glitch, as we saw here on this thread.

The video will make it very clear on what exactly is a glitch or not. However my intention is not to reopen discussion on various exploits and their bans or vice versa, I agree with what's currently banned and not banned in glitchless, for example. I just wanna point out that some exploits we call glitches, that I agree is banned in glitchless because it breaks the game too much, is not a glitch in it's definition.

For the curious, I just uploaded my video talking about what exactly is a glitch.

www.youtube.com/watch?v=LltT-BLcDDA

I think the main difference is,
Glitches are using Code-Behaviour to procure a result/reward that shouldn't work per Design,
while exploits are using a Mechanic as it was intended, but to an unintended Result.

For Dread, Glitches would include Pseudo-Wave and Water Bomb Jump.
Since as we learned here, the PWB ignores the shoot cancelation Layer of Walls by sticking the Beamcannon were it does not belong, and the WBJ creates a state to ignore the Gravitational Effect of the Water.

Good example for exploits would be Infinite Bomb Jump, for all Metroid without the 3 Bomb limitation. As well as some Wall Jump, as well as Shine Spark Sequences throughout the Franchise.

So in short:
Glitch - Underlying, Code-Based, Unintended Behaviour
Exploits - Visible, Design Based, Unintended Use

can we finally have a glitchless category now? please?

There's a un official leaderboard on the discord if anyone is interested.