The calling out of a statement with (usually gay) sexual connotation.
This is commonly done casually among males but any group of close friends will naturally do it.
E.x.
Richard: Man, I love how this big sausage just slides down my mouth
Jack: Yo bro thats mad Sus
E.x.
(Richard is washing a cucumber, twisting his hand as it moves up and down Jack: Yo bro what are you doing back there
Richard: Stroking my cucumber
Jack: Naaaaah thats mad Sus