The Big BANG Theory is a popular American sitcom that aired from 2007 to 2019. The show follows the lives of four socially awkward scientists and their neighbor, Penny, as they navigate life in Pasadena, California. The term 'The Big BANG Theory' refers to the scientific theory that states that the universe began with a massive explosion of energy. The crossword solution for this term is 'BANG', which is a four-letter word.