You in your pickup and I in my minivan are at opposite sides of the intersection of Main and Maple Street. I see you, you see me. Even tho I'm female, you understand the small upward nod I give you. My brothers told me it's guy-talk for "Hey, dude. You're doin alright" They also said it covers all social situations in which the receivee (that would be you) has had some troubles, and the nodder wishes to give encouragement, without gettin' all gushy about it.
A "small upward nod" = a useful social device. It wouldn't be a bad screenname, either.