(In a rocket or jet engine) a nozzle containing a central plug that widens towards the exit and then narrows, so that gas is expelled in a converging annular stream.
Origin
1950s.
Definition of plug nozzle in US English:
plug nozzle
noun
(In a rocket or jet engine) a nozzle containing a central plug that widens towards the exit and then narrows, so that gas is expelled in a converging annular stream.