Legal Definition of Invalid: (a) Not valid; illegal; void; having no effect. (b) A permanently incapacitated person | Looking for the legal definition of invalid? Learn what it means and its significance in the legal realm. Discover examples of invalid situations such as contracts, wills, and trademarks. Find out why understanding invalidity is crucial for business owners, including legal compliance, risk mitigation, and protecting intellectual property. Enhance your knowledge to make informed decisions and ensure a secure business environment