To tuck one's shirt only in the front, leaving the back to hang loosely. Named so because members of fraternities are often seen wearing their shirt in this manner. See: “popped-collar”, "classless"
That frat tuck goes very well with your pink shirt, popped-collar and flip-flops.
A recently popular shirt tucking technique primarily for males that usually involves the prominent showing of the belt buckle (extra points for scrolling LED belt buckles) that leaves the rest of the shirt untucked. Sometimes also referred to as the “one-handed tuck”.
Tucking your shirt in all the way around is too corporate and stiff. Try the ghettotuck. That shit is tight!