Buffalo

1: A type of animal

2: A city in New York

3: A verb meaning to fight

The only word that can be used to make one sentence:

Buffalo Buffalo Buffalo Buffalo Buffalo.
Buffalo (as in the city) Buffalo (as in the animal) Buffalo (as in the verb) Buffalo (as in the city) Buffalo (as in the animal)

In other words:

A Buffalo from Buffalo fought a Buffalo from Buffalo.

by Shay Live December 10, 2011