knight-errant

noun2

1. •
   A knight in a medieval romance who wanders in search of adventure and opportunities to prove his chivalry.
2. •
   A person who displays an adventurous or a quixotic spirit.

   • It had known and served all the men of whom the nation is proud, from Sir Francis Drake to Sir John Franklin, knights all, titled and untitled - the great knights-errant of the sea. — 1899