Someone who achieves the extra unecessary achievements, but does them in a half-ass fashion.
Patrick decided to be an Over-Under Achiever when he went the extra mile to do his extra credit, even though he already had a 103 percent in his english class. This project was done in a very UNorderly fashion. The rough draft write-up ended up having its title 'rough draft' erased and then replaced with 'Final Project'.
by E-bag March 30, 2010
Get the Over-Under Achiever mug.