Disarm is a warrior honor talent, available at rank 19 for Arms and Fury, and rank 22 for Protection. It removes the target's main hand and ranged weapons for 8 seconds. This has the effect of lowering a mob's damage, but usually shows a greater effect against players.
Disarm is typically used to the greatest effect against melee classes, or hunters. Disarm is of little use against casters since they almost never use their weapons.
Using this against a warrior or a rogue will be very useful, since most of their abilities require a melee weapon.
Disarm is very effective against hunters, as many of their abilities require a ranged weapon. It also prevents them from using abilities such as [Scatter Shot] and [Concussive Shot] to kite you. They will still be able to set traps however, so it is still a good idea to use [Hamstring] on the initial [Charge].
Patch changes
Patch 7.1.5 (2017-01-10): Re-added as an honor talent.