De Broglie is a proper noun that commonly refers to Louis de Broglie, a French physicist who is known for his work on wave-particle duality and the development of wave mechanics. While the term "De Broglie" is not typically used as an adjective or descriptor, some synonymous phrases could be "wave-particle theory," "quantum mechanics," "wave mechanics," or "De Broglie's hypothesis." These terms are closely related to De Broglie's contributions to the field of physics, and refer to the fundamental nature of particles as both waves and particles. Overall, synonyms for De Broglie tend to focus on the study of quantum mechanics, wave-particle duality, and the principles that drive these phenomena.