Satiety is the technical term. Not hard to see other words that are related - satisfaction, saturation; satiety is the point when we feel full from eating. Our challenge in this Western culture is that our sensitivity to that feeling has been blunted. (If you eat all they give you at a typical restaurant, you'll typically pass the healthy stopping point for satiety.)
This article gives a helpful look at 'feeling full'. They call it the 'hunger scale', rated from 0 = empty (those of us in the Western world rarely ever get here!) all the way up to 10 = Stuffed. (So, how was your Thanksgiving dinner?). The scale by itself is interesting and can be helpful, but the article continues with some thoughts on how to use the scale to train our ability to know when we are at a healthy state of 'satiety'.
As an aside, if you check out the "Blue Zones" study, you learn that, in the countries/locations where people live measurably longer lives, they generally eat until they are 80% full (think 7 or 8 on the hunger scale).
The article on feeling full gives three simple steps to see if your "fullness meter" needs re-tuning: 1. Rate your hunger before you start to eat; 2. Rate your hunger half way through the meal; 3. Rate your hunger at the end of the meal. Just paying attention to your feeling of fullness will heighten your awareness and sensitivity. If weight is an issue for you, it may help you to tune in to the 80% full feeling more accurately. Of course, what you are eating makes a difference in your ability to stop at 80% - check out some info on addictive food.