dull as ditchwater
"andy has a new girlfriend but i can't understand why, she is as dull as ditchwater  "wear the purple one, that black dress is dull as ditchwater" "
"very boring, or miserable
""andy has a new girlfriend but i can't understand why, she is as dull as ditchwater  "wear the purple one, that black dress is dull as ditchwater" "" What is the definition of "dull as ditchwater"?