1: A person who is motivated by their ideals. An intra-competitive person often marked by abandoning that which hinders their ideals.
2: One who strives for various degrees of near perfection.
3: Someone that desires more than is needed.
The over-achiever would not get married until she found the perfectfather for her future babies. She died alone in her early fifties.
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'.