When I was doing my application for MSU-COM, I called up their admissions office and asked them what I could put on community service. The woman I talked to told me I could put anything that I've done with any group or as an individual that has benefitted the community. She also told me to include things from high school (I was surprised by that, and not all schools will accept it.
On that note, if you had a leadership position in an org...that is not community service, BUT if your org had a golf tournament that donated money to some charity then you could count the time put into the golf tournament as community service. Does that make sense?
I don't know a definition. I tell my advisees that volunteering in a health care setting may not count to some adcom members. To me it's experience in a medical setting and maybe that alone. For community service, I give the example of my mother. She feeds homeless people once a week. THAT'S community service.