Retaliating specifically refers only to the inherent ability to deal Thorns damage to enemies when they Hit you. Some effects may cause you to deal Thorns damage in other ways, but those are not Retaliation, and effects which specifically care about when you Retaliate will ignore them.
Support gems

Barbs IAfter you Retaliate with Thorns Damage, you also deal your Thorns damage to enemies you Hit with Supported Skills.Deal your Thorns damage to the next 4 enemies Hit by Supported Skills after you Retaliate with Thorns

Barbs IIAfter you Retaliate with Thorns Damage, you also deal your Thorns damage to enemies you Hit with Supported Skills.Deal your Thorns damage to the next 6 enemies Hit by Supported Skills after you Retaliate with Thorns

Barbs IIIAfter you Retaliate with Thorns Damage, you also deal your Thorns damage twice to enemies you Hit with Supported Skills.Deal your Thorns damage twice to the next enemy Hit by Supported Skills after you Retaliate with Thorns

Quill BurstQuill Burst can only be triggered on Hit after you've
Retaliated with Thorns Damage.Supported Skills trigger Quill Burst on their next 3 Hits after you Retaliate with Thorns