“Pratipakṣa udaya” is a technical term used in Jain karma‑philosophy.

Break the words:

• Pratipakṣa = opposite, contrary
• Udaya = rise, fruition (when a karma starts giving result)

So pratipakṣa udaya means:

> The rise (fruition) of a karma that is opposite in nature to the karma that was previously active.

Because of this opposite karma rising:

• the effect of the earlier karma can be interrupted, reduced, or changed, and
• the soul starts experiencing a different, contrary result (for example, pleasant experience starting amidst previously painful experiences, or vice‑versa).

In simple words:

When one kind of karma is giving its result, and suddenly an opposite-type karma starts giving its own result, that new opposite rise is called pratipakṣa udaya.