Goosing someone is often considered a practical joke and works around the elements of surprise and humor. Goosing, while amusing, should ideally only be done to close friends or relatives, and definitely not to strangers.
The Action
Goosing involves a light grab or pinch of the buttocks, usually delivered from behind, and without being detected.
The Element of Surprise
An effective goosing includes the element of surprise. It is usually delivered at a moment the victim is not expecting it, and may be delivered in a public place but in such a manner that it is not witnessed by anyone except the person goosing and the person being goosed.
The Element of Humor
Humor is key in goosing. A goosing is not a malicious move, and is meant to amuse and surprise the person being goosed.