The phrase "damage buff" refers to a temporary increase in the amount of damage a character or weapon can deal in a video game or role-playing game. Full definition
Just kill NPC's and collect cystals for your ingame damage buffs and gold to spend in the arena (Crucible) area. (metacritic.com)
A bunch of weapon types are getting PvE damage buffs, and several perks (including Kill Clip and Dragonfly) are also getting buffed. (kotaku.com)
Maybe on boss fights like Fabricator and Malaphar, where you either get a huge damage buff or the boss gets its armor reduced, but on dummy parsing I think top performances are at about 12k, which means less of course on regular boss fights. (dulfy.net)