A dub is a person who will talk to you and be buddy buddy but then switch up on you and ghost you the next day.
Jon: Man, Samantha hasn't texted me back all day.
Keith: I been telling you she was a dub, man.
A full chest of something in Minecraft
This isn't a very broad word.
"We got a dub of potions"
"Why'd you brew so much bro"