filthy

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