Discuss and learn French: French vocabulary, French grammar, French culture etc.
Oh no, it's not slang.
it's an old french word.
it's used. in France everybody will understand.
two ways to use it, the second one is more used now :
- someone is "farfelu"
- a situation is "farfelue"
it means many things at the same time in one word : weird and strange and original and wild and fantastic and fanciful.