Everything what is not a Bitcoin lol.
If you see that devs of the project claim that their coin will be a new BTC because they have lower fees, faster transaction speed, better community and its price is currently undervalued so it should cost 10 times more so that's a shitcoin.
There is also a small shitcoin test. Their devs always like to say some loud words. So if you open their whitepaper, press ctrl+f and search for words like "revolutionize" and other loud words. If you found those words then congrats, that's a shitcoin.