Believe it or not, this sentence is grammatically correct and has meaning: “Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.” First devised by professor William J. Rapaport in 1972, the sentence uses various meanings and parts of speech for the term “buffalo” (and its related proper noun “Buffalo”) to make an extremely hard-to-parse sentence.
Although most people know “buffalo” as both a singular and plural term for bison, and “Buffalo” as a city in New York, “buffalo” is also a verb meaning “to bully, confuse, deceive, or intimidate.” Using these definitions, Wikipedia suggests the sentence can be read:
[Those] (Buffalo buffalo) [whom] (Buffalo buffalo buffalo) buffalo (Buffalo buffalo).
Still too hard to follow for those of us who don’t know “buffalo” as a verb. Refine once more:
[Those] buffalo(es) from Buffalo [that are intimidated by] buffalo(es) from Buffalo intimidate buffalo(es) from Buffalo.
And once more:
Bison from Buffalo, New York who are intimidated by other bison in their community also happen to intimidate other bison in their community.
Wikipedia has further explanation, including the slightly frightening note:
Buffalo is not the only word in English for which this kind of sentence can be constructed; any word which is both a plural noun and a plural form of a transitive verb will do. Other examples include dice, fish, right and smelt.
Beware of Buffalo buffalo, buffalo, for they may buffalo you.