The Brief: "Big mad" is an expression to indicate an individual is very angry.

DEEP DIVE
“Big mad” is an expression to indicate extreme anger in a situation. According to Urban Dictionary, the phrase is used when making fun of someone or trying to be annoying.
“Big mad” is the opposite of “lil mad,” which is less intense.
My story on the potential impact of a TikTok ban and how creators and users reacted this weekend to the news is on A1!!!!!!!! (The front page of NYT) https://t.co/6CgzbGOB3r
— Taylor Lorenz (@TaylorLorenz) August 3, 2020