You can defined it your way but my interest is to understand this>>> Are sports games or related competitive activities which stakes are involved between both sides or teams also gambling?
Remember, there would be a winner to be rewarded and a looser to lost the stakes.
In agreement to what other users have said already,
YES! is the answer to your question.
Gambling can be defined in different ways, with different words, which still mean the same thing. That's to say, gambling just means the same thing, no matter how it is defined.
An activity characterized by a balance between winning and losing that is governed by a mixture of skill and chance, usually with money wagered on the outcome.
I got that definition of gambling from an English-version-dictionary (Android-version) and the definition is selfexplanatory.
For example, if there is a fight between two students in a school and someone says that he or she is placing a bet that „student A“ will win the fight and another person also says that he or she is placing a money bet that „student B“ will win the fight, that is just a typical example of gambling. You can also set as many examples as you want, using other scenarios. As long as money is being staked and the end result would be a win or lose, that is just gambling.