A gesture with the thumb, index and middle fingers extended and raised in front of the head as a form of saluting.
In Britain and other British Commonwealth countries, a "two-fingered salute" refers to an Inward V gesture that is the equivalent of the Middle Finger. On Danbooru, a two-fingered salute is an actual Salute.
Not to be confused with Kuji-In, various Ninja gestures that may involve extending the first two fingers, but not as a salute, nor with V or V Over Eye, which have the fingers spread apart and are not salutes.