Libertarian is (to me):
1) Extreme political conservatism -- limiting the power and reach of government in almost every aspect. Most libertarians object to anything beyond protecting our borders and maintaining order in the streets.
2) Extreme fiscal conservatism -- minimize taxes, spending and government intervention in private enterprise.
3) No social conservatism -- this is what throws people about Libertarians. Many (if not most) support the legalization of drugs, abortions and many other issues social conservatives oppose. Even a deeply religious Libertarian wouldn't want to see their views mandated or even subsidized by other people.