A radiant smile is a facial expression that conveys joy, happiness, and contentment. It is often characterized by a wide grin, with the corners of the mouth turned up and the eyes crinkled in delight. The term 'radiant smile' can also be used to describe a person's overall demeanor, which is often warm and inviting. The crossword solution for the term 'radiant smile' is BEAM, which is an appropriate description of the expression. A BEAM is a ray of light that radiates outward from a source, and a radiant smile is a similar type of expression that radiates warmth and joy.