Limit Break
What is Limit Break?
Limit Break activate according to the number of Damage you receive (or more) and its Limit Break requirement value.
Example:
From the upcoming card from the Kai's TD06, Thunder Break Dragon's ability which is a Limit Break ability (see below), there is Limit Break (4). Which means the effect only activates when you have 4 or more cards in your Damage Zone. So if you got less than that value, that effect does nothing and will not activate.
TD06/0??
Thunder Break Dragon (サンダーブレイク・ドラゴン)
Dragon Empire/?/Narukami
Normal/3/Twin Drive!!/10000/-/1
Auto [?]: [Limit Break (4)] When this card attacks a vanguard, this card gets [Power] +5000 until end of that battle.
Auto: [Counter Blast (2)] When this unit is placed on [V], you may pay the cost. If you do, choose an opponent's grade 2 or lesser rear-guard and retire it.
So in future there could be other Limit Break value such as Limit Break (1), Limit Break (2), Limit Break (3) and even Limit Break (5).
Note: This is what is known so far, could be more or could be wrong. More information will be given and we will bring you the update after the Bushiroad Conference.