In Human design parts of your design are often talked about as being defined or undefined. Essentially when a part of your chart, either a center(a shape), a line (a channel) or a half line(a gate) is colored in it is considered defined. What this means is that the energy in this area or aspect of your character has a specific definition and your are designed to express that aspect in a consistent manner. You can draw and express this energy most if not all of the time.
For example, if you look at the chart of Natasha below, she has the gate 48, the half a black line coming off the Spleen going up to the throat. The gate 48 is about having depth and detail in the things you do. Since Natasha has this defined energy in her chart she is very likely to go into depth and detail in all the things that she does that she is inspired by. She will do this consistently.
The undefined areas in your design are the centers, the lines and the gates that are not colored in or are white. These areas are often also called open. In the undefined areas, you experience an inconsistent expression of that particular energy. In the presence of someone else carrying that energy you can amplify the expression. But on your on you experience that energy in an inconsistent way. If you look at the chart of Victoria below, she has an open or undefined Sacral center. The Sacral center is the main motor and source of energy to do things. Since Victoria’s Sacral center is undefined she will experience and express the energy to get things done in an inconsistent way. At times she may be Wonder Woman and really churn things out but at other times she may falter and lack energy to do anything.
We are designed to live out our defined energy. That is where we have consistent energy for doing and expressing. We are here to experience the undefined areas in unlimited ways but not to draw upon these areas in a consistent way. We are not constructed to run or draw energy through our undefined areas on a consistent basis. When one takes on living out the open or undefined areas consistently they are destined to have physical problems as these areas are not wired to handle the energy load.