1. the quality of being boring or uninteresting
2. the quality of lacking sharpness or brightness
3. the quality of being slow to understand or learn

Examples

• The dullness of the lecture made several students fall asleep.
• She complained about the dullness of her daily routine.
• The knife’s dullness made it difficult to cut the vegetables.
• The dullness of the gray sky matched his mood.
• His dullness in math class frustrated his teacher.
• The dullness of the paint made the room look dreary.
• Despite the dullness of the topic, she tried to stay focused.