In Jainism, "Siddhi Tap" is not a commonly used or classical term found in the primary scriptures or traditional lists of austerities (tapas). The word "Siddhi" generally means attainment, accomplishment, or spiritual perfection, and "Tap" (or "Tapa") refers to austerity, penance, or spiritual practices aimed at purifying the soul and reducing karmic bondage.

Jainism classically describes two broad types of austerities (Tapas):

1. Bahya Tap (External Austerities): - Anashana (fasting) - Unodari (eating less than one's fill) - Vritti-sankshep (limiting food items) - Ras-tyag (giving up favorite tastes) - Kaya-klesha (physical endurance) - Sanlinata (seclusion)

2. Abhyantar Tap (Internal Austerities): - Prayashchitta (repentance) - Vinaya (humility) - Vaiyavritya (service to monks and the needy) - Svadhyaya (study of scriptures) - Vyutsarga (renunciation) - Dhyana (meditation)

Siddhi, in the context of Jainism, is often associated with the ultimate spiritual achievement, that is, attaining liberation (moksha) and becoming a Siddha (a liberated soul who has destroyed all karmas).

If you are referring to a specific fasting or penance called "Siddhi Tap," it may be a regional or recent practice not found in canonical Jain texts, possibly designed to attain spiritual progress or accomplishment. Sometimes, local Jain communities or monks introduce new vows or observances with such names for the purpose of motivating laypeople in their spiritual journey.

In summary: There is no classical "Siddhi Tap" specifically listed in Jain scriptures. However, any austerity (Tap) that leads to spiritual accomplishment (Siddhi) aligns with the Jain path of self-purification. The ultimate goal of all Tap is to attain Siddhi, i.e., liberation.

If you have more context, such as a community or tradition where this term is used, please provide it, and I can try to elaborate further based on Jain perspectives.