IPA: /ˈhjuːmərlɛsli/
KK: /ˈhjuːmərlɛsli/
In a way that shows no sense of humor or fun; serious and without laughter.
She humorlessly pointed out the mistakes in the report.
Humorlessly → It is formed from "humor" (from Latin "humor", meaning fluid or moisture, which evolved to mean a mood or temperament) and "-less" (meaning without). The word "humorlessly" means without humor or lacking in a sense of humor.
Think of someone who is 'without' ('-less') a 'mood' or 'temperament' ('humor') — that's why humorlessly means lacking humor.