The term 'Upside-Down Frown' is a phrase used to describe a feeling of sadness or disappointment. The crossword solutions for this term are 'SMILE' (5 letters) and 'GRIN' (4 letters). Both words are used to describe facial expressions that indicate happiness or amusement. A SMILE is a facial expression characterized by an upward curving of the corners of the mouth, while a GRIN is a broader, more intense version of a SMILE.