Over the years I have had some very interesting answers to this question and I thought I would share some of them with you just to indicate the many answers there can be to this proposition.
First of all I have had some students ask "what do you mean by an elephant?" - now that, despite the snorts of derision from fellow students, is a pretty intelligent question and illustrates an important point when it comes to projects. Typically it is a question that is posed by those with some form of requirements analysis background. What do I understand from what you have said?
Having a clear and unambiguous understanding of the problem you can begin to devise a solution. If you think you know what the problem is and don't validate this with the customer you can very quickly charge off in the wrong direction. Avoid making assumptions, ensure clarity wherever possible.
My answer to this question has tended to be along the lines of "an elephant is a four legged animal, grey in colour, native to either Africa or India, a herbivore, notable for having tusks and a trunk, supposedly possessed of a prodigious memory".
That tends to satisfy the questioners - you may note that I have been careful in the definition provided and you may feel that something has been omitted, all will become clear in subsequent parts of this Blog.