noun1. the starting point for a new state or experience; "on the threshold of personhood " 2. the smallest detectable sensation 3. the entrance (the space in a wall) through which you enter or leave a room or building; the space that a door can close; "he stuck his head in the doorway" 4. the sill of a door; a horizontal piece of wood or stone that forms the bottom of a doorway and offers support when passing through a doorway 5. a region marking a boundary