Something invincible is victorious over everything. Disease, death, destruction? No match for something truly invincible. Mere humans who imagine they're invincible, however, will inevitably prove that they're not.
Invincible comes ultimately from the Latin verb vincere, "to conquer." Many of the uses for invincible are for describing someone or something victorious or unbeatable at what they do. A company can be invincible when it outsells similar businesses for years, a tennis player is invincible after winning all of the majors in a year or a career, and Superman and the Indomitable Snowman are invincible as long as they stay away from kryptonite and the warm sun.