Interesting to know that one of my favorite activities has a name, even a following! I lived in Walla Walla, WA for 6 years, four of those years attending Whitman College and racing for the Whitman College Cycling Team. Walla Walla is home to, I believe, some of the best road riding in the country. It's an endless maze of quiet, rolling country roads (and some good climbs, should you ride far enough) in every direction and it only ever takes 5 minutes to get out of town. Perfect.
So I would ride, ride, ride around Walla Walla-- picking up new roads, collecting them like tokens, in a push to "collect them all." Once I ran out of paved roads-- naturally, I would need to collect the rocky kind. Without second-guessing, I would point my 23mm tires onto dirt and go. What I had was a BIKE and bikes are-a-made for ridin'! It never occurred to me that I "shouldn't" or "couldn't" ride my "road racing bike" (the only bike I had) (wow.. there was a day when I had only one bike?? anyway..) on fire road. I just did it-- and it was GREAT fun!
Sure, I slipped and swam-- fishtailing through the deep gravel, bumping over the big rocks. But that was the fun! Whereas on the road, I let my mind wander-- on the gravel, I had to FOCUS. Going uphill required finesse to keep the tire from slipping, going down demanded an understanding that brakes are not always the answer-- and often a yelp in frightened glee.
But this is, "under-biking" you say? Fabulous. Sounds good to me!