This is the 3017th most frequent Dutch word.
bokser
A "bokser" is a boxer (a person who practices the sport of boxing).
Here, 'bokser' is used to describe an athlete participating in the sport of boxing.
De bokser won de wedstrijd overtuigend.
The boxer won the match convincingly.
In this instance, 'bokser' refers to a type of clothing, specifically boxer shorts.
Jan draagt een bokser als pyjama.
Jan wears boxer shorts as pajamas.
Uncommonly, 'bokser' might metaphorically or humorously be used to describe a goat ('bok') when jumping, but this would require contextual explanation.