[nhaehnle]

A curious "definition" I once read (sorry, don't remember the original source) goes something like this. Mathematics is the smallest subject that satisfies the following:

1. Mathematics is the collection of topics for which there is a mathematician who considers the topic part of mathematics.

2. Mathematicians are those humans who devote their lives to expanding human knowledge of mathematics.

3. Mathematics includes geometry and arithmetic.

[murbard2]

Source: http://arxiv.org/pdf/math.ho/9404236.pdf