It's scientifically defined (Woods, 2023).

https://doi.org/10.1080/03626784.2023.2272988

I propose a definition of shitposting that embodies four distinct elements: a reliance on absurdity or “meaninglessness,” the critique or disruption of online discourses, the employment of an “internet ugly” aesthetic, and the use of meta-languaging.

Meaninglessness/absurdity - There's no intrinsic meaning in the content, but there is in said content's circulation. Shitposts "mock", "denigrate", "construct an image of authenticity", and "accrue social capital" (he probably means upvotes or Discord reactions)

Disruption - It can be used politically, e.g. the alt-right drowning out opponents, or just plain derailment, using "ironic references... to confound commentary or analysis" (he uses a Twitter example in the article -- i.e. among the "Here's what I did today!" there's a Jon Arbuckle of in of out, and it disrupts your train of thought)

Internet ugly aesthetic - Kinda obvious. Motion blur on a plastic bag sort of stuff. But he diagnoses an internet-queasiness I didn't know I had: "[shitposting] provides a critique of the overly streamlined information ecosystem of the internet... an imposition of messy humanity... on smooth gradients, blemish correcting Photoshop, and AutoCorrect"

Meta-languaging - Well, memes evolve. It's part of their meaningless-content meaningful-use interaction. Like a meme with a random Subway sandwich on it, obviously insanely edited over repeatedly.

Actually a really interesting read. The man quotes dril and talks about how he started a small movement where "corncobbing" was an insult.