Attempting a precise definition of Friedrich Nietzsche's Superman is a daunting task, as Nietzsche was not a philosopher in the traditional sense - he did not build all-encompassing philosophical systems, nor did he feel the need to explain himself in detail. He was more of a poet, applying metaphor and painting grand visions, and often expressed himself in paradoxes. Thus, a variety of interpretations of the Superman can be put forward, but perhaps they can all be summed up into this quote from Zarathustra: "Man is something to be overcome."
The Superman is better than man. This characteristic, although very vague, must be included in any description of the Superman, as it would be absurd to assert that a being that is in some sense inferior to modern man were the Superman. The Superman is perhaps more human than the modern human being - his human characteristics are stronger, and he does not have the need to restrict them with the slave morality of Christianity. For Nietzsche, the most important of these characteristics is, of course, the Will to Power. The Superman strives to attain power, and does so without trying to hide his lust for power as the modern man. It must be pointed out, though this is subject to debate, that the power the Superman strives for is intellectual, philosophical power. Nietzsche sees the history of philosophy as a power-struggle, and the Superman takes this to a new level, as he understands and admits he is partaking in a philosophical battle for power.
This philosophical war, which Nietzsche often praises metaphorically, is a battle for values. The Superman defines his values and his whole reality as he pleases, freeing himself from the slave morality of Christianity. A hatred of Christianity is one of the key characteristics of Nietzsche's writing, and thus the Superman is the logical conclusion of his thought.
Nietzsche's spiritual home was antiquity and not 19th century Germany, and the Superman was also his rebellion against the modern world. He hated such modern phenomena as democracy, socialism and nationalism, for he was an individualist in the extreme, and felt that these "modern ideas" were an impediment to the flourishing of brilliant individuals. The Superman, utterly unmodern, is the ultimate Greek aristocrat, because he is an ethical and metaphysical ruler ("The real philosophers (Supermen) are commanders and lawgivers..").
On the other hand, the Superman is Nietzsche's attempt to save people from nihilism. It should be pointed out that, contrary to what many think, Nietzsche was not exactly a nihilist - he admitted that in a sense nothing mattered, that neither truth nor right or wrong existed, but he wanted humanity to rise up from the nihilistic darkness of the death of God, and create a good and bad, create a human meaning for existence (Nietzsche does not approve of the term 'evil' - the title "Beyond Good and Evil" refers to moving from the good and evil of Christian slave morality to the good and bad of an aristocratic master morality). The Superman's values are secular and human, and his highest value is the furtherance of human life. However, the Superman accepts the inherent tragedy of existence and the importance of suffering. "What does not kill me, only makes me stronger."