Lol another one of those threads.
Allright, let's do a quick google!
Gambling definition:
1. play games of chance for money; bet.
2. take risky action in the hope of a desired result.
Investment definition:
1. the action or process of investing money for profit or material result
Game definition:
1. a form of play or sport, especially a competitive one played according to rules and decided by skill, strength, or luck.
2. a type of activity or business, especially when regarded as a game.
You can see from this that all 3 words can apply to each other. This means that when you're gambling you're always investing and in most cases you're also playing games (poker, dice, roulette, slots, sports, etc).
Good definitions, however,
I think that gambling can be called a game for sure, as it is an activity. While it is a risky game, it is still a game.
However, I don't think gambling can be called an investment in the slightest, as you aren't "investing" your money per se. You could regard it as one, but it would be foolish.