I feel kinda silly but...

Non-scale victory. That is, something about your weight loss that isn't directly about lowering the number on the scale. For example, fitting into an old pair of jeans or being able to take a flight of stairs without being short of breath.

For instance, a favorite shirt or pair of pants fits more loosely than before.

The "must reads" post at the top of the Getting Started board has a pretty good list of the common acronyms used on MFP if you're looking for any others: http://community.myfitnesspal.com/en/discussion/1069278/acronyms-and-terms-for-new-mfp-members-v-6/p1