Exposé is referred to as
Application Windows in the Keyboard shortcut preference window, and
App Exposé in the trackpad preference window.
To activate it press ctrl and down arrow
You can verify that they are in fact the same thing just with different names by pressing ctrl and down arrow and observing that it has the same behavior demonstrated in
App Exposé of the Trackpad preference pane (4 finger swipe down )
I get the impression that App Exposé is moving the way of the dodo because App Exposé came unchecked by default on my 10.8 install. (Also, Mission Control is just so much more useful than Exposé)