Salty

means that you get hella pissed, annoyed, or upset because of some little thing that someone else does even though its not that deep and is just a joke

Boy:"its just a joke man why do you have to get so salty about it"

or
Boy:"i dont want to pick liam"
Friend:"why not"
Boy:"he gets so salty when he loses"
or
Boy:"why so salty"