v. To flick one’s finger (or the act of doing so), by bracing it against and snapping it away from the thumb, often euphemism or simile for encouragement
This may be a dismissive gesture, be used to indicate a direction, or to discard probuscine effluvium
If I do, fillip me with a three-man beetle.
— Falstaff, Henry IV part 2, by William Shakespeare (1599)
Faithful horoscope-watching, practiced daily, provides just the sort of small but warm and infinitely reassuring fillip that gets matters off to a spirited start.
— Shana Alexander, “A delicious appeal to unreason” (2005)
Etymology: Appearing in the 15th century, it seems simply to remind one of the sound that the gesture would make