From door +‎ jamb.

doorjamb (plural doorjambs)

1. Either of the upright posts on either side of a door, which together support a lintel.
   • 2022, Liam McIlvanney, The Heretic, page 123:

     There was a ball-pein hammer on a ledge above the doorjamb and Kidd reached up softly and took it down.

• doorpost

• jamb

• doorframe