If something is invigorating, it makes you feel well, awake, and full of energy — a cold swim, mountain air, a brisk walk, a lively class. It can lift the mind as well as the body: an invigorating conversation leaves you keener, not just less tired. It is the -ing adjective from invigorate, to give vigor (British spelling often vigour): strength and energy. Slightly bright and approving; advertisements like it. Though actually, vigorous and invigorating are not the same. A vigorous person already has energy; an invigorating swim gives you energy. One describes who is strong; the other describes what pours strength into you.