A an expression coined in urban UK, meaning "put a lid on it" or shut that mouth fast before some hears you.

-Mister Kingsley Price of capthatt.com

#keepquiet #shutup #shut up #shut your mouth
Jenny, "So as I was telling you about Abigail, she had this thing in her hand that smelt like..."
John, seeing Abigail round the corner; "Capthat!"
by gifty7 September 12, 2018