/
ˈθrɛʃəʊld, 
ˈθrɛʃˌhəʊld/
n.
  - a strip of wood or stone forming the bottom of a doorway and crossed in entering a house or room.
 - a level or point at which something starts or ceases to happen or come into effect. 
▸the level at which one starts to feel or react to something:
 a low pain threshold.
 
Etymology
OE therscold, threscold; first element rel. to thresh (in the sense ‘tread’).