That's because it's about as well defined as the boogey man or a hate crime.
The well known goal of globalism is one world government. No borders, no sovereignty, multi-culturalism, and no middle class, all to secure the position of the elite for all time.
That’s about as well as I can define globalism.
I don't think globalism is all that hard to define or understand.
It's a notion that attempts to describe and quantify the degree of interconnectivity between nations---the interconnectivity of each nation's economies, cultures, political structures, languages, infrastructures, laws and legal traditions, etc., and the degree to which one nation bears responsibility (or does not bear responsibility) for other nations. A globalist, for example, would champion this interconnectivity, and work towards institutions and structure to strengthen it, while an anti-globalist would not champion this interconnectivity (or champion it to a lesser degree), and would not work towards institutions and structure to strengthen it.
I'd argue that more or less, it's the notion of "are you your brother's keeper?" on a global scale.