Noun
A band round the crown of a hat; sometimes, a band of black cloth, crape, etc., worn as a badge of mourning.
Source: Webster's dictionaryAfter a quick, Red Bull-fueled rehearsal session in the PTA room with her gum-smacking, neon Reebok-ed backup dancers, school security guards escort Lil Mama to the field, clad in a white “Smooth Criminal” fedora with a rhinestone hatband. Source: Internet
If you want to change it up without trading up, try weaving your own hatband. Source: Internet