Chad is often used in the context of voting to describe the leftover pieces from ballot cards. They had to recount the chads to ensure the accuracy of the vote.
Pro Tip 2/3
2000 Election
The term became famous during the 2000 US presidential election due to disputes about ballot counting. The 2000 election was notorious for the controversy over hanging chads.
Pro Tip 3/3
Rare Outside US
Use of 'chad' in the voting sense is uncommon outside of the United States. In my country, we use electronic voting, so the concept of a chad is foreign to us.