When someone talks so much shit and you want them to shut up. You tell them to "Flush it"
Adam: Im the man. I can get any woman I want and I can rock her world for hours non-stop
Lydia:Oh Just FLUSH IT already!!
an expression used to chide or mock someone who has just embarrassed his or herself, or been embarrassed, as a satirical encouragement.
man 1: "you two ladies look great, is she your mom?"
woman: "...she's my sister" *both walk away
man 2: "OOOH FLUSH IT"