When it comes right down to it, it is fairly hard to come up with a concise, yet satisfactory, definition of "conservative." For one thing, like liberal, the word can be applied to more than just the political sphere; there are social conservatives, "conservative" chess players, etc. It might be easier to define conservatism as trying not to do anything stupidly risky, things that fly in the face of common sense, that defy the testimony of God in nature and Scripture, that flout history, that ignore the fallen and depraved nature of mankind; as an approach to life and governance that seeks to limit government to the role laid out for it by God, thereby establishing justice and protecting Man's God-given rights. A conservative, then, would be a person who practices conservatism, especially when it comes to governance.
Two things will be seen immediately: first, that conservatism relies implicitly upon a biblical worldview. In my opinion, this is the principal thing that distinguishes it from libertarianism, which shares many of the same positions concerning man's rights, but lacks an adequate intellectual basis for defending them, and therefore results in some most impractical and imprudent positions. Second, that conservatism is not implicitly wed to one particular form of government, though it might be said to be devoted to one particular governmental aim, the fulfillment of its God-given role as minister of justice. Many putative conservatives these days operate on the assumption that conservatism is inseparable from Western-style representative governance, but this is not the case. The first noted conservative of relatively modern times, for example, Edmund Burke, was a committed monarchist. Granted, he favored the unwritten constitution of England, which guaranteed certain rights to all Englishmen, but he was a monarchist nonetheless. A conservative will not make the mistake of thinking that one can govern Baghdad the same way that one governs Amarillo.
This explanation suffers from being too brief, but it will have to suffice.