Definition
To act humourlessly means you're serious, without any amusement or joking. It's like delivering bad news with a stone-cold face 😐. Think of a judge sternly giving a sentence, or a teacher scolding a student. It implies a lack of lightheartedness, even when a bit of levity might be appropriate. Someone responding humourlessly might also miss a joke completely. The opposite of humourlessly would be playfully or jovially.