There are many words in English that have unique meanings or nuances that may not have direct equivalents in other languages. Here are a few examples:
Serendipity: Finding something good without actually looking for it.
Quirk: A peculiar aspect of someone’s character or behaviour.
Mellifluous: Sweet-sounding, pleasant to the ears.
Cacophony: A harsh, discordant mixture of sounds.
Lackadaisical: Lacking enthusiasm or determination; carelessly lazy.
Surreptitious: Kept secret, especially because it would not be approved of.
Gobbledygook: Language that is meaningless or hard to understand; jargon.
Defenestration: The act of throwing someone out of a window.
Lagniappe: A small, unexpected gift or bonus.
Are there any words I have missed? Perhaps in another language you speak, there are some English word for which there is no direct translation? Let me know!