B1
not interesting or exciting in any way; boring
Dictionary examples:
The history lecture was so dull, even the clock fell asleep. (0.0)
The meeting was so dull, even the coffee fell asleep. (0.0)
The textbook was so dull, it could cure insomnia. (0.0)
She wrote dull, respectable articles for the local newspaper. (49.2)
He's pleasant enough, but deadly dull. (52.2)