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Merriam Webster Dictionaries define the word "dissipation" as:
An act of self-indulgence especially : one that is not harmful : amusement
Whereas Oxford Learner's Dictionary define the word as:
Living a life of harmful but enjoyable activities
Now I want to ask why Oxford Learner's Dictionary define the "activities" as harmful where as Merriam-Webster do not.
This is an amusing contradiction.
The core meaning of the word "dissipation" is a wasteful action.
This leads to its most common sense: "gradually disappear or be lost as waste"
The fins on the engine dissipate heat.
Dissipation of the oil slick took over three weeks.
From this we get the derived sense of "an activity that is amusing but unproductive", or "a hedonistic way of living". These are not actively harmful, but passively cause harm, as the person isn't living a productive life.
This derived sense is now rather old-fashioned:
Dissipations such as card games and partying ...
Going to a party is not itself harmful, but if you go to parties every night, your work and grades will go down. So going to parties is not actively harmful, but does cause harm in the long run.
On the other hand, something that is directly harmful would not be called a dissipation. Taking heroin would not normally be called a dissipation. It is actively harmful.
Merriam Webster have picked up on one aspect, "a dissipation does not do active harm", Oxford have picked up on another "a dissipation wastes your potential and does harm in the long run".
A learner will very rarely come across this sense of dissipation. (The "waste heat" or "slowly disintegate" meanings are much more common). I would recommend not using "dissipation" in this sense, as it is rather dated.
