knight errant 
noun (plural knights errant)
A medieval knight wandering in search of chivalrous adventures.At last, Don Quijote decides to seek honor and glory and fulfill his duty (to right wrongs), and become an actual knight errant....
- After years of obsessively reading books of chivalry, his mind finally snaps and he decides to become an actual knight errant like those in the tales he has read.
- A favourite subject of literature and folklore, at one extreme he appears as a knight errant, driven on by a desire for honour and sense of adventure, while at the other he is a bully and a braggart.
Derivatives
knight-errantry
- Together with his absurd cowardly squire Crabshaw, and his horse Bronzomarte, the half-mad Launcelot undertakes a quixotic life of knight-errantry, warring against the enemies of virtue and reason.