1. An improvident activity in which winning gleefully proceeds losing. 2. The saddled process of chasing one's loses or blowing one's winnings. 3. Chinese finger cuffs. 4. An insatiable itch erroneously believed to be satisfied by scratching. 5. The willingness to ask Chance for Certainty.
Horse race betting, casinos, sports betting etc, are all forms of gambling. There are many more of course, all which basically get the same results.