What is a furlong?

A furlong is a distance equal to 220 yards, one eighth of a mile.

Nowadays it is most often used in relation to horse racing.

The name possibly comes from a contraction of furrow-long - the length of a furrow that a team of oxen would plough. A set of these furrows a chain (22 yards) wide would take the team of oxen a day to plough and this area ploughed (a furlong by a chain) is called an acre (though an acre itself, as a measure of area, can be any shape).

It can also be a last name.