Someone humourless is too serious. They do not laugh at things other people find funny, and they may not see a joke even when it is kind. It is a criticising word: you are saying this person has no sense of humour, or will not allow one. You can also call a face, a voice, or a meeting humourless when the feeling is dry and tight, with no play in it. This is the British spelling, with the u in humour. American English writes humorless; the meaning is the same. Though actually, people sometimes call someone humourless just because the joke was mean or the moment was wrong — so listen for whether the speaker is being fair.

沒有幽默感的、一本正經的（英式拼法；美式寫 humorless）