Humourlessly means doing something in a humourless way: too seriously, with no laugh and no play. Someone may speak humourlessly, answer humourlessly, or shake their head humourlessly. The idea is the same as humourless — not able, or not willing, to laugh at things other people think are funny — but this form tells you how the action happens, not what the person is. It is not a common everyday word. People more often say without smiling or with no sense of humour. The spelling follows British humourless; American English would write humorlessly.