Was in my car, in the neighborhood, almost to my house. Two teens were throwing a football back and forth on the street. When they saw me approach they moved off the street, and as I drove by each one they raised their arms with their hands about 3 feet apart and slightly above their heads, the elbows bent. As if holding a large beach ball over their heads. I gave each a gentle wave and a friendly nod.
Never saw that gesture before. Must be generational.
Anybody have any idea?
its the touchdown signal.
You scored!
Were their palms facing each other? Did they separate to opposite sides of the street, by chance? If so, they’re definitely saying your car was a football, and your “kick” was worth points.
Sounds similar to an invitation to violence type posture. Or maybe a “wtf” type gesture.
Both would be accompanied by foul looks or language so I’ll go with fieldgoal gesture as well.
Are you from the US? If so, it’s highly unusual if you are, it’s highly unusual you’re not familiar with the touchdown stance.
If you are from US and are familiar with the touchdown stance, eliminating it as a probability, were their shoulders pulled up around their head? If so, it’s highly likely to be WTF stance as K2500 stated, especially if they were mouthing, What The F***!.
Another possibility is an exaggerated Ayyyyy… ala Fonzie! 
Again, not a positive gesture.
“Car!” or “Game Off!”
The guy hiding in your backseat was pointing his gun at them.
Interesting answers so far, but I’d guess that’s maybe the most likely. That or the “touchdown signal”. They were on the the same side of the street, palms facing each other. Facial expressions not the least bit hostile, almost like they thought it was funny.
Yeah, from the US. Not a sports fan. At all. Well, I used to be in to baseball till about age 15 or so. Never cared for football…ergo, my ignorance.
I imagine it’s safe to say it wasn’t gang signage.
Palms facing in, definitely a touchdown signal! Good to know they were having fun with you!
Edit: Had to double-check, actually more likely meaning field goal or extra point. Yeah, I’m not a sports fan either! 
They’re all the same signal.
A touchdown requires the signal of only one judge. An extra point or field goal requires two: to watch either goal post to see if the ball passes within.
mc
FYI - most gang signs are hands only, not broad gestures, AFAIK.