gate, door, vestibule, point, edge, borderline, scepter, start, brink, room access, doorway, sill, doorstep, entrance, limen, origin, doorsill, verge, sceptre, wand, inception, outset.
I felt it the moment his foot crossed our threshold-
Seeing me on the threshold,
he looked up and smiled.
When she reached her own house again, Mrs. Bolton called to her from the kitchen threshold
as she was passing the corner on her way to the front door: Mis' Putney's b'en here.