Quilt or quilted maple refers to a type of "figure" in maple

Maple

Acer is a genus of trees or shrubs commonly known as maple.Maples are variously classified in a family of their own, the Aceraceae, or together with the Hippocastanaceae included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favour inclusion in...

 wood. It is seen on the tangential plane (flat-sawn) and looks like a wavy "quilted" pattern, often similar to ripples on water. It is a distortion of the grain pattern itself. Prized for its beauty, it is used frequently in the manufacturing of musical instrument

Musical instrument

A musical instrument is a device created or adapted for the purpose of making musical sounds. In principle, any object that produces sound can serve as a musical instrument—it is through purpose that the object becomes a musical instrument. The history of musical instruments dates back to the...

s especially guitars. Quilted maple is an end grain figure that shows a circular pattern on flat sawn material. There are many terms that describe the shape and pattern of quilted maple. Aka popcorn, tubular, sausage, bubble wrap, angle step.

High quality (3A grade or above) quilted maple can be extremely expensive. A standard guitar billet made of 5A (premium) quilted maple costs a few hundred dollars.