Definitions for "Nerf"
If one profession is superior to the other available professions then the developers (in this case Blizzard) can choose to "nerf" the profession by taking away what ever it is that makes them so good.
To reduce the effectiveness of a certain item, profession, skill, etc. by developer fiat
Usually used in reference to making a skill or item less powerful than before
Keywords:  bump, freindly, nascar, shove, bumper
To bump or shove another car in an oval-track race.
To bump lightly against another car, usually from behind and often on purpose, as a warning or a bit of psychology. Very common in NASCAR racing.
a freindly tap from bumper to bumper, making a vehicle aware of your presence. Commonly used in desert racing when a faster vehicle is approaching a slower one on a narrow stretch.
Keywords:  gimp
Similar to gimp
a reduction in an ability to the point where it is no longer useful, i
To soften or reduce an ability, item, player, or action. Usually this is a term applied when a power or ability is reduced because it is perceived to be too powerful.
When an ability/item/character class have its stats decreased or gets worse in any way it's nerfed.
Keywords:  downgrade, softer, less, rules, link
( link / ) To make a rules element significantly less powerful (sometimes too much so).
To downgrade, to be made softer, or make less effective. "X has been nerfed."
North East (North America) Rainbow Family; formerly, New England Rainbow Family.
Keywords:  economy, research, new, fund
New Economy Research Fund.