A European binary with knock in (ebaki) option is a European Binary option with an American knock in barrier.
For this option you set two barriers: one for the underlying European binary option and the knock in barrier (that must be hit in order to activate the underlying option).
The fixed payout specified in the option is only made if, on the option's expiry date, both the following facts are true:
The knock in barrier has been hit during the option's life.
The underlying European binary is in the money.