vocal laxative

When one person says something that instantly triggers someone else to start spewing words from their mouth hole.

Jessie: Did you hear Jessica and Bobby broke up?
Andrea: Oh my god yes!! But that's okay because I don't think she was right for him. But at the same time he was really nice, and cute, and nice. So maybe they were good together. But maybe not. Did you hear about Brian and Jenna?
Jessie: Wow. I didn't mean to give you a vocal laxative.