Patrick Schwarzenegger -- He'll Flip You Off With Meaning

If Arnold Schwarzenegger's 18-year-old son gives you the finger, you could misread the whole thing if you believe it's a showing of solidarity with his dad.

Patrick Schwarzenegger hit up Tattoo Mania in West Hollywood -- soon after his big high school graduation -- and tatted up his middle finger with a small letter "A ."

The "A" does NOT stand for Arnold -- something that would be significant given Arnold's potent dalliance with his housekeeper -- something that ripped Patrick's family apart.

We're told the A actually stands for "A-squad" -- a nickname for Pat's group of friends -- and Pat got it done to remember the good ol' days after he ships off to USC in the fall.

Patrick is young, so he's entitled to believe that he will actually still care about his high school friends in 5 years.