swag·ger ( swá ger) v.

swag·gered swag·ger·ing swag·gers v. intr.
1. To walk or conduct oneself with an insolent or arrogant air; strut.
See note at strut . 2. To brag; boast. v. tr. 1. To browbeat or bully (someone). n. 1. A swaggering movement or gait.
2. Boastful or conceited expression; braggadocio. [Probably frequentative of swag ] swag “ger·er n. swag “ger·ing·ly adv

Relating to Tennis, often times certain Players are said to walk on the Court with a swagger which is physical display of confidence. Could be misguided however it can give that Player the psychological edge they need to win.