Former Secretary of Defense Donald Rumsfeld is EXPLAINING his TSA pat-down at Chigago's O'Hare airport this week ... chalking the whole thing up to some bionic body parts!



After TMZ posted the photos of Rummy  getting his pat-down on Wednesday ... Donald went to his Twitter page (yes, Donald has a TWITTER page!!) and dropped the following statement:

"It takes those of us with two titanium hips and a titanium shoulder a bit longer to get through TSA ..."

Then, Rummy actually LINKED to our TMZ article!!

That's right ... we got a direct line to a guy who used to kick it at the Pentagon! 

We bad.

No one is immune to the probing hands of the TSA ... including former Secretary of Defense Donald Rumsfeld ... who got the pat-down at Chicago's O'Hare airport this afternoon ... and TMZ has the pics.



Sources at the airport tell TMZ ... Rummy was all smiles during the body sweep and was "very nice" throughout the procedure.

We're told several people recognized Donald ... and at one point, he waved to a group of soldiers who were dressed in their military uniforms.

Eventually, TSA agents cleared Rumsfeld and he was allowed to travel like everyone else ... ever so slightly violated.