Mrs. Grundy is a character from Thomas Morton's play 'Speed the Plough' (1798). She is a symbol of a narrow-minded, puritanical figure who is overly concerned with propriety and convention. The term 'Mrs. Grundy' has come to refer to someone who is excessively concerned with social conventions and propriety. The crossword solution for the term Mrs. Grundy is 'PURITAN', which is an appropriate description of her character.