The term 'speak monotonously' can be broken down into two crossword solutions: 'DRONE' and 'INTONE'. The word 'DRONE' is a noun that refers to a continuous low humming sound, usually made by an engine or other machinery. It can also refer to a person who speaks in a dull, monotonous voice. The word 'INTONE' is a verb that means to speak in a monotone or sing in a monotone. Both words are used to describe speaking in a dull, monotonous way.