Derived from the term "thootie thursday" a thootie is an outfit worn once a week where both components of an outfit (i.e. sweatshirt and sweatpants) are matching in color. The basic thootie is gray on gray, however, "thootie" is a loose term which can be applied to a variety of different outfit combinations. For example, a dark blue shirt worn with dark blue jeans to school may still be considered a thootie even though it does not conform to the original thootie thursday of strictly sweatshirts and sweatpants as originated by the Princeton High School Winter Track Team.
Sarah: "Guess what tomorrow is?"
Sarah: "Wrong. It's thootie thursday!"
Emily: "Yess! I cannot wait to sport my pink sweatshirt and matching pink sweatpants!"