I think that colloquially, people use the word "gamble" to mean a wide variety of things.

One might consider gambling anything that involves any risk of losing money. I feel this definition is too wide because it includes activities like.. investing in mutual funds.

Another might consider gambling only the activities in which return is based entirely on luck.

Neither fits with an official webster definition, but unless we agree exactly on what a term means, it doesn't seem meaningful to say whether something is or is not an example of that term...