Definition of ad-libbing:
(n) :
(debating) advantage
(n) :
(tennis) Advantage; also, designating the left-hand side, from the player's point of view, of their half of the court, where the advantage point following a deuce is always played.
(adv) :
(often punctuated) Initialism of Anno Domini (borrowed from Latin); in the year of our Lord. [In the year of our Lord (often abbreviated A.D. or AD).]
(n) :
(film) Initialism of assistant director.
(n) :
(military) Initialism of air defence or air defense.
(n) :
(pharmacology) Initialism of antidepressant. [(pharmacology) An agent that prevents or counteracts depression.]