Tod: Yeah they should nerf him in the next version he's to good.
Imba can be applied to a subject in gaming (Weapon, army, race, role or job) which can be either too strong (Overpowered, or OP) or too weak (Underpowered, or UP).
Although the word IMBA can be applied to both OP and UP, it is mostly used to describe an in-game subject which is too strong.
A good example for imba is the job hunter in Ragnarok Online.
"Stop using Counterspells and Dark Rituals they're so imba."