A wont is a custom or habit, like my wont to drink at least ten cups of coffee a day. (In this particular example, some people might call my wont an addiction.)
Wont is a tricky word, in terms of pronunciation; some people argue it sounds like want, while others insist it's pronounced like won't. Perhaps the confusion over pronunciation explains why this word is used relatively infrequently in everyday speech. It's most people's wont to use a synonym like custom or habit.