The crossword solution for the term 'Rival of Alexa' is Siri, which is a virtual assistant developed by Apple Inc. Siri is an intelligent personal assistant that uses voice recognition to respond to questions and commands. It was first released in 2011 and has since become one of the most popular virtual assistants on the market. Siri is a direct competitor to Amazon's Alexa, and both are used for a variety of tasks such as playing music, setting reminders, and providing information.