Someone who is fortitudinous shows great courage, strength of mind, and resilience in the face of pain or adversity. Whether it's finishing a marathon or climbing to the top of a mountain, these feats require a fortitudinous spirit.
Fortitudinous is the adjective form of the noun fortitude, "the mental and emotional strength to endure great difficulty." Both words come from the Latin fortis, meaning "strong," which is actually also where we get the word fort, "a strong place built to withstand an attack." A fortitudinous person is sort of like the human version of a fort, but the word doesn't just describe soldiers in battle. It describes a person or actions that are steady, brave, and enduring under pressure, even if that's just having the quiet strength to get through a crisis or a long, hard day at work.