A panahara pachakhan usually refers to the Jain vow of Panahara Upvas. In simple words, it is a fasting vow in which a person abstains from solid food, and in some traditions it is associated with taking only water or liquids during the vowed period. It is a form of pachkhan because pachkhan means a formal vow or resolve in Jainism. ( jainknowledge.com)

In Jain practice, this vow is taken for self-discipline, purification, and spiritual focus. ( jainknowledge.com)

If you meant a specific form like Panahar Upvas nu Pachkhan, I can explain its exact meaning in simple Jain terms.