Hunda Avasarpini Kaal in Jainism means an irregular or distorted descending half-cycle of time. In this period, the normal pattern of the Avasarpini becomes unequal, exceptional, or abnormal, and unusual events are said to occur. ( jainfoundation.in)

In simple words:

• Avasarpini = the descending time cycle.
• Hunda = irregular / uneven / atypical.
• So Hunda Avasarpini = a deviated form of the descending time cycle. ( jainfoundation.in)

If you want, I can also explain the 6 aras of Avasarpini Kaal in simple Jain language.