Knockback

Knockback is a game mechanic that pushes a player or mob away when they are hit.

Increasing knockback

 * enchantment
 * enchantment
 * potion
 * - ability applies large knockback to all mobs in a radius.

Knockback Resistance

 * - provides immunity to knockback from mobs.
 * (Pet Item) - provides immunity to knockback.
 * - ability provides immunity to knockback.
 * - knockback immunity while riding.
 * Rotten Armor - Gain additional  knockback resistance to arrows.

True Knockback
True Knockback is a type of knockback that ignores all anti-knockback items. It's similar to, but applies to knockback.

Sources:
 * Non-Dungeon bosses:
 * Ender Dragon's Fireball attacks
 * Revenant Horror and Sven Packmaster's anti-cheese attacks
 * Dungeon mobs:
 * Some of Thorn's minions deal true knockback
 * Lost Adventurer's "Dragon's Breath" Ability
 * Defend Jerry's Workshop Magma Cubes' attacks

Tips

 * Knockback on weapons is generally disliked by players as pushing your enemy to far away simply causes it to take longer to kill, making chain hits more hard to get. In most cases the default knockback applied by weapons is considered sufficient.