At the very basic level - the word civilization has a definition. Loosely used, it'd talk about an area, group or period. These parameters would be distinguished, in the mind of the person using the term, by striking continuities in ways of life, thought & feeling.
There was a term that I ran into a while back - collective self-differentiation. This is as much a verb as it is a noun.
Those groups of people having progressed from the Verb usage to the noun application are termed as civilized. Somehow - this word, defies a clear definition.
Come to think of it - it is easier to define a civilization as compared to civilization.
Has it ever struck you - that civilization's damned dangerous?