Question: What is a comprehensive definition of Philosophy? Alternatively, is it impossible to define Philosophy? This is a pseudo-[meta](https://philosophy.meta.stackexchange.com/) question, but it seems like it belongs here.

Answer: 
I think Wittgenstein is very illuminating in this respect. Some relevant quotations, dealing with some aspects of the question (PI stands for *Philosophical Investigations*):

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> PI§109 [...] Philosophy is a battle against the bewitchment of our intelligence by means of our language.
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> PI§126 [...] One might also give the name "philosophy" to what is possible *before* all new discoveries and inventions.
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> PI§127 The work of the philosopher consists in assembling reminders for a particular purpose.
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And as far as philosophy speaking of itself posing a problem:

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> PI§121 One might think: if philosophy speaks of the use of the word "philosophy" there must be a second-order philosophy. But it is not so: it is, rather, like the case of orthography, which deals with the word "orthography" among others without being second-order
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In general I highly recommend anyone troubled by the question 'What is philosophy?' to read PI§89-138 - one of the most brilliant self-reflections on the purpose and nature of philosophy in the history of thought. Of course you have to be minimally aware of the context of Wittgenstein's thought, but I feel these passages are elucidatory nonetheless.
Philosophy is just a word, like many others. As a 'science' it has no scope, and it's entirely based on the difficulties we have in understanding our own language. Look around, there are no genuine philosophical problems. We define words, like "soul" or "God" and then, we talk endlessly about them, that's Philosophy.