An obvious and common definition is the feather of a large bird, often a goose or turkey, formed into a pen by pointing and slitting the lower end of the barrel.
A plectrum formed of a feather for plucking the strings of a musical instrument; in instruments of the harpsichord type, a piece of crow quill set on a jack and put into motion by the keys.
A float of a fishing line made of a quill,
A convenient way to pick the teeth.
Threads wound on a quill, ready for the weaver.
To form small, cylindrical plaits or folds, to goffer thus using papers or fabrics, or ribbons or lace. Would you like to quill a ruffle for your cap? You do wear one, do you not? Lacking many quills I offer a modern day substitute - just smooth out your fabric strip while wet, place a series of plastic drinking straws over and under the strip and let it dry.