1. He's not the sharpest tool in the shed.
2. She's a few cards short of a deck.
3. He's a bit slow.
4. She's a complete idiot.
5. He's really dumb.

Fact
Nine U.S. Presidents never went to college: George Washington, Andrew Jackson, Martin Van Buren, Zachary Taylor, Millard Fillmore, Abraham Lincoln, Andrew Johnson, Grover Cleveland, and Harry Truman.      .. More >>