Date: 14th century
a. not clean or pure <dirty clothes> b. likely to befoul or defile with dirt <dirty jobs> c. contaminated with infecting organisms <dirty wounds> d. containing impurities <dirty coal> 2. a. morally unclean or corrupt: as (1) indecent, vulgar <dirty jokes> <a dirty movie> (2) dishonorable, base <a dirty trick> (3) unsportsmanlike <dirty players> b. acquired by disreputable or illegal means ; ill-gotten <dirty money> c. disagreeable, distasteful, or objectionable but usually necessary (as in achieving a desired result) <hired a thug to do their dirty work> 3. a. abominable, hateful <war is a dirty business> b. highly regrettable <a dirty shame> c. likely to cause disgrace or scandal <dirty little secrets> 4. foggy, stormy <dirty weather> 5. a. of color not clear and bright ; dullish <dirty blond> b. characterized by a husky, rasping, or raw tonal quality <dirty trumpet tones> 6. conveying ill-natured resentment <gave him a dirty look> 7. having considerable fallout <dirty bombs> • dirtily adverb • dirtiness noun Synonyms: dirty, filthy, foul, nasty, squalid mean conspicuously unclean or impure. dirty emphasizes the presence of dirt more than an emotional reaction to it <a dirty littered street>. filthy carries a strong suggestion of offensiveness and typically of gradually accumulated dirt that begrimes and besmears <a stained greasy floor, utterly filthy>. foul implies extreme offensiveness and an accumulation of what is rotten or stinking <a foul-smelling open sewer>. nasty applies to what is actually foul or is repugnant to one expecting freshness, cleanliness, or sweetness <it's a nasty job to clean up after a sick cat>. In practice, nasty is often weakened to the point of being no more than a synonym of unpleasant or disagreeable <had a nasty fall> <his answer gave her a nasty shock>. squalid adds to the idea of dirtiness and filth that of slovenly neglect <squalid slums>. All these terms are also applicable to moral uncleanness or baseness or obscenity. dirty then stresses meanness or despicableness <don't ask me to do your dirty work>, while filthy and foul describe disgusting obscenity or loathsome behavior <filthy street language> <a foul story of lust and greed>, and nasty implies a peculiarly offensive unpleasantness <a stand-up comedian known for nasty humor>. Distinctively, squalid implies sordidness as well as baseness and dirtiness <engaged in a series of squalid affairs>. II. adverb (dirtier; -est) Date: circa 1931 in a dirty manner: as a. deceptively, underhandedly <fight dirty> b. indecently <talk dirty> III. verb (dirtied; dirtying) Date: 1591 transitive verb 1. to make dirty 2. a. to stain with dishonor ; sully b. to debase by distorting the real nature of intransitive verb to become soiled
New Collegiate Dictionary. 2001.