What does filthy mean?
Filthy is an adjective denoting an extreme degree of dirtiness — far beyond everyday mess — and is one of English's most versatile words for the repugnant. Physically, it describes grimy rooms, squalid conditions, or unwashed clothing; figuratively, it labels obscene language and indecent material, as well as moral corruption, most famously in the phrase 'filthy lucre,' a long-standing expression for money gained dishonourably. In informal usage, filthy can even become hyperbole in the opposite direction: 'filthy rich' wryly characterizes extravagant wealth as if wealth itself were a kind of stain. The word derives from filth, its parent noun, and carries a stronger charge than plain 'dirty' precisely because it implies disgust rather than mere untidiness. Its force makes it a favourite in vivid description, comedy, and moral commentary alike, which is why writers reach for it whenever mild language would undersell the squalor.
Extremely dirty or unclean; disgustingly foul.
"After working on the engine all day, his hands were absolutely filthy."
Obscene, indecent, or morally repugnant; used especially of language, material, or money.
"The comedian's act was full of filthy jokes that had the audience howling."
In this sense, 'filthy lucre' specifically denotes money acquired dishonestly.
'Filthy rich' isn't an insult about hygiene — it's a centuries-old jab suggesting that great wealth is inherently dirty, and English speakers have never stopped using it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of filthy
Filthy originates from Old English fȳlþ, meaning filth or corruption, formed from the root behind the adjective fūl ('foul'). The derived form emerged in Middle English as filthe-related adjectival usage and settled into its modern spelling by the early modern period. It shares deep Germanic roots with related words for corruption and impurity, and its figurative extension to money — 'filthy lucre' — entered English through the Tyndale Bible translation's rendering of a phrase in the pastoral epistles, cementing the association between dirt and ill-gotten gain.
Related word forms
How filthy is actually used
Filthy is emphatic and informal-leaning; 'dirty' is the neutral choice for ordinary grime. The figurative senses carry strong disapproval — obscene language, corrupt money. 'Filthy rich' is a well-established, often playful term for extreme wealth.
Easily confused with filthy
Filth is a noun naming dirt or obscene material itself, while filthy is an adjective describing something covered in or characterized by that dirt.