The once obscure term "chad" is now in the news of late because of the 2000 presidential election recounts. Machine recounts are higher than the original counts because chad is more likely to fall off the more times the ballots are run through the machines. Apparently there are five types of chad. In a hand recount, the first three would be counted as legitimate votes, but the last two would not

Hanging door: one corner hanging off
Swinging door: two corners hanging off
Tri-chad: three corners hanging off
Pregnant: the chad bulges but is not punched through
Dimple: the chad is indented

Source: http://www.cnn.com/2000/ALLPOLITICS/stories/11/12/chad.derivation/

Chad is also the name of a 7th century saint from Ireland who was the Bishop of Lichfield. He is also known as Ceadda.

Almighty God, whose servant Chad, for the peace of the Church, relinquished cheerfully the honors that had been thrust upon him, only to be rewarded with equal responsibility: Keep us, we pray thee, from thinking of ourselves more highly than we ought to think, and ready at all times to give place to others, (in honor preferring one another,) that the cause of Christ may be advanced; in the name of him who washed his disciples' feet, even the same thy Son Jesus Christ our Lord, who liveth and reigneth with thee and the Holy Spirit, one God, now and for ever.

Source: http://elvis.rowan.edu/~kilroy/JEK/03/02.html