George Zimmerman -- He Threatened Me with a Gun ... Motorist Claims

George Zimmerman flashed a gun at the motorist who fired a shot into Zimmerman's car ... at least that's what the motorist is telling his lawyer.

Matthew Apperson's lawyer, Mark NeJame, tells TMZ, his client did NOT flash his headlights at Zimmerman Monday nor did he chase him down. NeJame says Apperson ended up side-by-side with Zimmerman when the famous former defendant waved a gun.

NeJame says it was pure self-defense, buttressed by the fact that Apperson is the one who initiated the call to 911. He actually had to hunt someone down who had a cellphone because he didn't have one at the time.