In addition to its normal attacks, the Ghorgon may make an additional special attack at an Initiative of 1. This attack has the Killing Blow special rule, but To Wound rolls of a 4+ act as Killing Blow attacks, instead of just rolls of 6.
Source: Warhammer Armies Project: Unofficial 9th Edition (v2.2)
In addition to its normal attacks, the Ghorgon may make an additional special attack at an Initiative of 1. This attack has the Killing Blow special rule, but To Wound rolls of a 4+ act as Killing Blow attacks, instead of just rolls of 6.