-staff-line thickness. The shape of the background is determined by
-@code{whiteout-style}. Usually @code{#f} by default.")
+staff-line thickness. The @code{LyricHyphen} grob uses a special
+implementation of whiteout: A positive number indicates how far the
+white background extends beyond the bounding box in multiples of
+@code{line-thickness}. The shape of the background is determined by
+@code{whiteout-style}. Usually @code{#f} by default. ")