This is the 3250th most frequent Japanese word.
寒い
Cold.
寒い is used as an adjective to describe the temperature or weather.
今日はとても寒いです。
It is very cold today.
寒い is used here again as an adjective, comparing temperatures between the room and outside.
この部屋は寒いですが、外ほどではありません。
This room is cold, but not as much as outside.
寒い is metaphorically used here to comment on humor, implying that the joke was 'cold' or not funny.