This is the 7203rd most frequent French word.
mulder
"Mulder" is not a standard French word. It may refer to a name or require clarification.
In this sentence, 'Mulder' is used as a proper noun referring to a specific individual's name.
Mulder est le personnage principal de la série X-Files.
Mulder is the main character of the X-Files series.
Here, 'mulder' might be referenced not as the proper name, but as a slang term assuming it has one, contextualized as a new vocabulary item.
J'ai appris aujourd'hui ce que signifiait mulder en argot.
Today I learned what mulder means in slang.
In this construct, 'mulder' is symbolically used as a noun describing someone who is inquisitive or investigative, inspired by the character traits associated with Mulder from the mentioned series.