The phrase "tight bun" refers to a hairstyle where the hair is gathered tightly and neatly at the back of the head, resembling a round bun shape. Full definition
And it's always «strong character muscles» (and not tight buns or thick wallets) that will help you to achieve this esteemed mission! (mindbodygreen.com)
For the hair, we kept it simple and polished; a low tight bun. (kinddistinction.com)