What does it mean if your stress test is negative?

"negative" is good. A "negative" stress test means the absence of what is being tested for--i.e. No signs of flow-limiting blockages in coronary arteries. In other words, the heart muscle is getting plenty of blood flow. It's important to note that a normal stress test does not mean the absence of underlying non-obstructive coronary disease. Detecting this may require other tests, depending on your risk profile.
No Ischemia. A stress test is a test designed to detect the presence of myocardial ischemia. Ischemia occurs when there are blockages in the arteries. These limit the amount of blood that can get to the heart muscle. When you exercise that muscle needs more blood, if it can not get adequate blood it becomes ischemic and this is what stress tests are designed to detect.A negative test means no ischemia detected.