What is your definition of occasional and regular use?

This one friend and I were getting into a little "debate" about what defines occasional cannabis use. I don't put myself in the heavy category, yet I smoke at least once every two weeks. It depends on many things such as if I have bud, if I'm going to a place where there is bud or if I just feel like smoking. I'm definitely not a habitual blazer. Anyway, my friend likes smoking herb. He's new to it but he still feels somewhat guilty whenever he lights up. In situations where the topic of marijuana comes up in conversation with a group of friends, he either denies or downplays his usage. He's been smoking quite a bit recently, pretty much to the point of 3 to 4 times a week but he denies that he is a heavy user. I didn't really accuse him of heavy use, but I did tell him he's certainly not a weed virgin anymore.

I realize that the definition of occasional and heavy use varies from person to person. However, I do believe that there is some type of average that we all can agree upon. Is a person a heavy user if they smoke 5 times in one day but only every other week? Is a person an occasional user if they smoke only on the weekends every weekend? Is it dependent on concentrations of THC in the body? I just wanted to know what you blades thought of this. I was always curious how frequency came into play when people say "I smoke weed" or "I don't smoke weed (but only occasionally)".