This definition is now used at the Festival of Quilts (source: Innovations Officer):
Quilts that are minimalist with a clean, modern design that provides a feeling of space, often achieved by the use of negative space, and with strong visual impact. They often use asymmetry, improvisational piecing with a reinterpretation of traditional blocks or the quilt lacks a visible block structure. They are machine or hand quilted in a way that is sympathetic to the design.
Listed below are a few links to other definitions of and discussions about 'what is a modern quilt?". Please be aware that, at this point, you will be taken out of the Guild's website to a wholly independent websites that are not linked to the Guild.