When someone swashbuckles, they fight with a sword in a very fancy and exciting way, like in a movie.
Swashbuckling is usually seen as fun and adventurous, like a hero in a story.
Examples:
The pirate swashbuckles with his sword on the ship.
She loves to watch the hero swashbuckle in the movies.
He swashbuckles through the crowd, looking for the bad guy.
The cat swashbuckles with the feather toy.
The knight swashbuckles with the dragon, saving the princess.
He swashbuckles his way to victory, defeating the enemy.