The comedian's subtle humor often went over the heads of the younger audience.

subtle 是形容词，意思是"微妙的、难以察觉的"，指那些需要仔细体会才能理解的幽默或含义。这个词来自拉丁语 subtilis，原意是"精细的、纤细的"。 go over one's head 是个习语，字面意思是"从某人头顶越过"，比喻"超出某人的理解能力"。