Definition of "brio"

He lay tossing restlessly on a dirty old straw palliasse, and was in great pain; but greeted his friend with a dash of the old brio.

1917, Henry Handel Richardson, Australia Felix, Part II Chapter I

And as if to undermine their authority still further, Welsh Philpott in his innocence has made the error of placing Rick beside the pulpit in the very spot from which in the past he has read us the day's lesson with such brio and persuasion.

1986, John le Carré, A Perfect Spy