I’d be very much interested on native speakers comments on the term. I read it in statements of British and South African accounts. It is sometimes used like a pejorative, but there is even a Wikipedia article on it. From the pictures, it looks a lot like mountain hiking, up to sac_scale T6. But not requiring the extra glacier gear.
I can comment on this from my perspective. In American English, “scrambling” is an outdoor activity in between hiking and climbing. A scramble is a route that ascends up some rock. Ascending the route will require the use of your hands (at the very least for balance, and possibly also to help propel you upwards). A rope is not typically used, because the risk of falling is lower and the consequences of a fall may be less dire (though a fall can still be very dangerous).
In the Yosemite Decimal System for rating climb difficulty, a “scramble” is a Class 2 or Class 3. I believe that in the UIAA system a scramble is a Grade I or Grade II, but I have less familiarity with that rating system so perhaps someone else can confirm or correct that.
I found this photo on Wikimedia Commons which I think illustrates “scrambling” pretty well. You can see from the people’s posture that the slope is not vertical; it’s probably closer to 45°. They are using their hands on the rock in front of them for balance, but loosing grip on a handhold probably wouldn’t cause a catastrophic fall like it might in rock climbing.
I live in a mountainous part of the U.S., and “scrambling” is a pretty familiar term in the outdoor communities here. It’s not uncommon for hikes (especially those whose destination is a summit) to end in a scramble. Some people aren’t comfortable with that sort of thing, and others are specifically seeking it out, so trip reports and guidebooks will almost always mention whether a peak requires scrambling to reach or whether it’s a “walk-up”.
In my area, most of these scrambles are currently mapped as highway=path in OSM. Usually the way that represents the walkable trail goes all the way up to the summit, ignoring a transition from walking to scrambling in the final few hundred feet. I think it would be great if this last segment of the journey were tagged differently so that specialized renderers could display this information. And I think it would be best if the tagging for the scrambling portion did not use highway=path, so that non-specialized renderers wouldn’t imply that there is a walking route to a summit when in fact none exists (and scrambling is required to reach the top).
My preference would be to use the existing tags for climbing routes to tag scrambles. I think that set of tags is already designed to cover this use case, it just hasn’t been widely applied yet. A way can be tagged climbing=route along with climbing:grade:uiaa=1 to indicate an easy scramble, or climbing:grade:uiaa=2 to indicate a more difficult one. Other scales (like YDS) can also be used if they’re more appropriate for the local context.
The benefit that I see for using these tags rather than creating a new category for scrambling is that the boundary between scrambling and climbing can be quite fuzzy, and it’ll be hard to define that boundary for OSM’s purposes in a way that is verifiable. By using the climbing tags, we can make this distinction using the standard climbing rating that are already in widespread use in the outdoor community.