Incapable of being conquered or subdued; that cannot be overcome; unconquerable; insuperable: as, an invincible army; invincible difficulties.
                  
                
                  
                    noun. 
                    One who is invincible. Specifically
                  
                
                  
                    noun. 
                    A member of an Irish society, organized in 1881, whose avowed object was “to remove all tyrants from the country.”