What does "fortitude" mean?

Fortitude: That strength or firmness of mind which enables a person to encounter danger with coolness and courage, or to bear pain or adversity without murmuring, depression, or despondency; passive courage; resolute endurance; firmness in confronting or bearing up against danger or enduring trouble. Extolling patience as the truest fortitude. Milton. Fortitude is the guard and support of the other virtues. Locke. See Courage, and Heroism.