In Jain usage, kalpvasi generally means those who live according to a disciplined, restricted way of life during a religious period, especially in Chaturmas or Paryushan.

A kalpvasi typically:

• stays in one place for a set period,
• follows strict vows and simplicity,
• practices samyak acharan like fasting, prayer, swadhyay, and repentance,
• reduces worldly activities and attachments.

In some traditions and regional usage, the word is also used for devotees who reside near a temple or religious place during a sacred period and live a very austere Jain life.

So, in simple words, kalpvasi are Jain devotees who voluntarily adopt a highly disciplined, spiritual, and restrained lifestyle for religious merit and आत्मशुद्धि.

If you want, I can also explain the meaning of kalpa, chaturmas, and how kalpvasi tradition is observed in Jainism.