Repeatability is the ability of a component to repeat producing the same result under the same conditions. With an object placed at 30cm, does a distance sensor always produce a voltage of 1.62V? If you collect samples of the voltage, you can extract statistics from the samples.
A high repeatable sensor produces samples that have a small variance. This is a very useful feature because it means you can take very few reading, or just one, in the application. A sensor with poor repeatability needs many samples, or you have to operate with a lot of uncertainty.
How about ``digital'' sensors, such as look-down sensors? Even though the end result is boolean, these sensors are inherently analog. In other words, you can still measure the output voltage of a divider bridge using a phototransistor using a fixed source of IR illumination. Fortunately, most phototransistors are very repeatable.