Basically, what it implies ... trim that angles down and away from the room,
instead of up and toward the room.
CAVEAT: It might well be a regional thing.
Around this area, you see the term used for trim on the bottom of wall
cabinets, where the top part of the trim stands out from the cabinet and
tapers back toward the wall at the bottom ... the "reverse" of what crown
molding does at the juncture of wall and ceiling.
I've also seen the term used when using multi-part crown molding in room,
and the bottom part, or profile, is also used as the baseboard (at the
juncture of the wall and floor).
YMMV, depending upon where you live, IME.
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