Definitions:
concentrated on a single subject or into a short time; very thorough or vigorous

(of an adjective, adverb, or particle) giving force or emphasis.

denoting a property which is measured in terms of intensity (e.g. concentration) rather than of extent (e.g. volume), and so is not simply increased by addition of one thing to another.

an intensive adjective, adverb, or particle; an intensifier.