Unreasoning zeal refers to an excessive and intense passion or enthusiasm for a particular cause or idea without logical reasoning or thought. Some synonyms for unreasoning zeal include fanaticism, extremism, fervor, obsession, and mania. These terms imply a lack of control and balance in one's emotions and actions, often leading to extreme behavior and rhetoric. Other similar words include zealotry, radicalism, dogmatism, and intolerance. It is important to approach passionate beliefs with a level of reason and critical thinking, as unbridled zeal can lead to dangerous and harmful ideologies.