What's he mean by "spilling tea?" Is this an idiom?

Native speaker’s answer
Rebecca
"Spilling tea" is actually slang! It means to share gossip or intriguing drama. "Spill the tea" is the common phrase to use. This is considered "Gen Z" slang, those born between 1997 and 2012, but is used by a few generations! So here he's made a pun using the phrase since he's drinking coffee. Ex: Spill the tea, sis. What happened at the party? Ex: I have some tea to spill for y'all. Ex: My friends and I just spill tea whenever we meet for lunch.