Knockback

Knockback is an ability in Diablo 3 that will knock enemies off of their feet and send them flying backwards. The damage and distance enemies are sent back, depends on how powerful the Knockback ability being used is.

Knockback can be used as an Offensive Ability, keeping enemies at a distance and while destroying them with powerful ranged attacks.

Knockback can also be used as a Defensive Ability in many situations. If you are low on health and being swarmed by a group of monsters, knocking them back a few yards can give you that extra time you need to get to safety. This is especially useful for the Ranged Classes that cannot take as much damage as the Melee Classes. (The Diablo 3 Ranged Classes include the Demon Hunter, Witch Doctor and Wizard and the Diablo 3 Melee Classes are the Barbarian and Monk).

Knockback has the opposite effect of Pull. 

The Following Is A List Of Each Class' Skills That Can Knockback Enemies Or Have A Chance To Knockback Enemies:

Barbarian Knockbacks

Bash
Cleave (Scattering Blast)
Ignore Pain (Bravado)
Leap Attack (Toppling Impact)
Ground Stomp (Avalanche)
Revenge (Grudge)
Furious Charge
Seismic Slam
Ancient Spear (Rage Flip)
Sprint (Gangway)
Wrath of the Berserker (Arreat's Wail)

Demon Hunter Knockbacks
Impale (Impact)
Vault (Rattling Roll)
Rain of Vengeance (Stampede)

Monk Knockbacks

Fists of Thunder
Lashing Tail Kick
Lashing Tail Kick (Vulture Claw Kick)
Lashing Tail Kick (Sweeping Armada Kick)
Tempest Rush

Witch Doctor Knockbacks

Gargantuan (Wrathful Protector)
Wall of Zombies (Pile On)

Wizard Knockbacks

Wave of Force
Spectral Blade (Impactful Blades)
Magic Weapon (Force Weapon)
Unstable Anomaly (Passive Skill)

Follower Knockbacks

Scoundrel (Powered Shot)
Enchantress (Forceful Push)