Dà cuō 大撮 "Big Pinch" or just 撮 (abr. 早) “Pinch”
Use the thumb and the middle finger to pluck two strings that have four strings between them in a closing motion, fingers moving toward the palm. This sounds an octave when played on a pentatonic tuning. If using own nails, nail and pad of the fingers touch the strings.
Kao also offers the term “kou”.