  We have investigated the domain wall (DW) dielectric response of potassium
dihydrogen phosphate (KH2PO4) crystal under 0-500V dc-bias electric field.
Activated DW-contribution onsets freezing at Tf({\omega}, V), some 27K below
the ferroelectric TC; timescale {\tau}f(T, V) exhibiting Vogel-Fulcher (VFT)
divergence. Sharply distinct low- and high-field behaviors of TC(V), DW-Tg(V),
VFT-T0(V), barrier energy Ua(V), and DW glass-fragility m(V) signify a
field-induced transition from randomly-pinned/vitreous to
clustered/glass-ceramic phases of domain wall matter. Field-hysteresis
({\epsilon}'poled > {\epsilon}'unpoled) observed at high dc-bias indicates
coexistent unclustered DW phase, quenched-in during the field-cooling. We
construct a paradigm T-E phase diagram depicting the complex glassy patterns of
domain wall matter.
