The act of correcting a person for their inapropriet actions, for stepping over the line, to show your dominance over them, or to let them know their place with you. Similar to correctiing a dog on a slip collar. It involves a brief correction, typically involving something other than your fist or hand, like a stick, belt, pipe, tire iron, or cane. This is not a full on beating, asskicking, or fist fight, just one or two hits with the tool of choice to let them know they don't want anymore.
Son: Come on pop I'll get the tire iron from my truck and well give him an attitude adjustment.
Here is part of the song from Hank Williams Jr. - Now I've got this big old Brother-in-law
And me and him just never did get along
Cause he just wasn't treating my sister nice.
He got drunk one night and started and beating me up
And I went and got a tire tool out of my truck
And straightened him out as cold as a block of ice.
It was an attitude adjustment and it'll work every time.
An attitude adjustment-I made him see the light.
Now he says I'm his kind of man,
He comes around me with his hat in his hand
It was an attitude adjustment; I cured his family pride.
Prior to 2009 when WWE introduced new PG rules, the move was officially known as 'The F-U', a play on Brock Lesnars somewhat simlar finisher 'The F-5'.