Wearing a ponytail tied up and secured away from one side rather than the back. Akita Neru and Kaga (Kantai Collection) are noted wearers of this style.
Side ponytails should not be tagged ponytail. Ponytail specifically refers to a ponytail at the back of the head (topic #4101).
The following tags are aliased to this tag: sidetail, side_tail (learn more).