Outdoor slave training teaches the slave to respond as desired in a external location, often in public. Slave training is designed to make the slave act as their Master or Mistress wishes: being submissive, holding posture, or displaying their status as a sex object.
Training outdoors can be done in a spacious, concealed location such as parks, farms or even the Master or Mistress' back yard. This often provides more space for training than inside, and allows the slave to learn obedience as they stand in the rain, or sit pool-side exposing their nakedness.
In public, this can be as simple as requiring the slave to use the name "Master" or "Mistress" while there is the risk of being overheard. More complex training is possible, with the presence of unaware strangers adding an extra dimension to the intensity of the training.