Knockback refers to the repelling force that causes brief loss of control to the subject when being propelled. This force can be easily demonstrated with a tornado (such as one summoned by a Tempest Locket or a Colosseum twister-type Summoning Stone). Although knockback may appear to be a direct result of damage (due to almost always being accompanied by damage), this is not so. Because of this, there are a few subtleties surrounding knockback that may be worth noting.
For example, if a hero is wearing the crown, losing the crown is not a direct result of taking damage; it is possible to retain the crown despite taking damage, just as it possible to lose the crown without taking any damage at all—it is simply dependent upon knockback and its degree of force.
One of the finer examples of the subtleties of knockback can perhaps be observed with Cultist Zealots and Wizard's Static Barrier. When a Cultist Zealot is killed, it will explode, causing four projectiles to emerge but also a small radius of knockback. The Static Barrier protects against most damage, but not knockback. That said, if a Cultist Zealot dies but has not exploded yet, and Wizard places a Static Barrier on top of its body, Wizard (or anyone standing close enough to the body) may be pushed out of the barrier via knockback when the Cultist Zealot explodes. This can become critical information when depending upon the protection of the Static Barrier particularly where Cultist Zealots are in great numbers.