(as) dull as ditchwater

Very boring or unexciting. This phrase is often used to describe a person. My date with Dave was not great—he is as dull as ditchwater. I fell asleep during that movie because it was as dull as ditchwater.

If someone or something is as dull as ditchwater or as dull as dishwater, they are very boring. He's a dull writer and that's a fact. Dull as ditchwater. `Most of the politicians in Ontario are dull as dishwater,' he said. Note: The expression `dull as ditchwater' is over 200 years old, whereas `dull as dishwater' is a more recent variant. The reference is to the dull dirty colour of the water in ditches or in washing-up bowls.