I find the use of "off-normal" to be funny. I give them credit though, because all of these four levels are still officially considered part of the "Emergency Classification" even with the use of the term "off-normal"
1. Notification of Unusual Event (NOUE) often just mentioned as an "unusual event"
2. Alert
3. Site Area Emergency (SAE)
4. General Emergency - This is the highest level of emergency available for a nuclear plant (Fukushima like event) and I find it funny (I believe no accident) that they appear to use the word "general" to downplay the seriousness, much like above using "off-normal" to describe emergency classification events of concern.
Here is the official link to the NRC for more detailed information. Please note that for nuclear materials and fuel cycle facility licensees, there are different alerts. These can be found at the same link, here:
http://www.nrc.gov/about-nrc/emerg-preparedness/about-emerg-preparedness/emerg-classification.html