A sad feeling felt on Saturday night, where you feel like you should be out having fun and making memories but instead you are stuck at home doing nothing. Big Sad Saturday's make you feel stuck with thr choice of wanting to go out despite nothing to do or nowhere to go, or be bored at home even though you don't feel like watching a movie or doing anything.
"Hey Ralph, how was your weekend?"
"Sunday was nice. Unfortunately, I had a Big Sad Saturday."