Jain Dharma is not an acronym, so it does not have a “full form” in the usual sense.

It means:

• Jain = follower of the path of the Jinas (victors over inner passions)
• Dharma = righteous spiritual path, duty, and religion

So, Jain Dharma means the religion and path taught by the Jinas, especially the Tirthankars.