Being extremely sad / depressed.
I failed my German test. Now I have the big sad...
"My mom had a stroke" "Big big sad dude. I hope she's okay"
Pretty self explanatory. When you more than sad, but less than depressed, you are BIG sad. When you BIG sad, you cry very loud, hence *crying noises intensify*
You: OMG IM SO CLOSE TO WINNING!!!!
Mom: BRUHHH turn your computer off.
You: Why would I turn my computer off?
Mom: BRUHHHHHHHH I turns the wifi off LOL
You: NOOOOOOOO
Mom: LOLOLOLOLOLOLOLLOL
You: BIG sad *crying noises intensify*