The phrase "be knocked unconscious" can be substituted with a variety of synonyms that convey similar meanings. Some options include being rendered unconscious, losing consciousness, being knocked out, passing out, being stunned, or being felled. These phrases typically connote a sudden and forceful blow to the head or body that causes temporary loss of consciousness. Other related terms could include being incapacitated or disabled, though these may not specifically imply loss of consciousness. Ultimately, the choice of synonyms depends on the context and intended connotations, whether discussing a boxing match, a medical emergency, or a fictional narrative.