threshold threshold /ˈθrɛˌʃoʊld/

noun

1. () The starting point for a new state or experience  ( threshold )
   the starting point for a new state or experience
    On the threshold of manhood
   on the threshold of manhood
   
2. () 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  ( doorsill , doorstep , threshold )
   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
    Watch your step as you cross the threshold into the house.
   Watch your step as you cross the threshold into the house.
   
   
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  ( room access , threshold , doorway , door )
   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
   he stuck his head in the doorway
   
4. () The smallest detectable sensation  ( limen , threshold )
   the smallest detectable sensation
   
5. A region marking a boundary  ( threshold , brink , verge )
   a region marking a boundary
     The mountaineer carefully approached the edge of the cliff, teetering on the brink.
   The mountaineer carefully approached the edge of the cliff, teetering on the brink.