Does a spell with Repeat count as one spell or multiple spells when interacting with Defy?

Ruling: A spell with Repeat counts as a single spell, so it can be countered by one Defy regardless of how many times it repeats.

Nuances:

• The combined mana cost of the original spell plus Repeat costs does not prevent Defy from countering it
• Repeat provides value by getting multiple effects from one card, but this comes with the vulnerability of losing all repeats to a single counter