Answer: nixie

AnswerCrossword Clue
NIXIE

Undeliverable letter

NIXIE

Germanic water sprite

NIXIE

Undeliverable letter, in post-office slang

NIXIE
Undeliverable letter, to postal employees
NIXIE
Undeliverable mail
NIXIEWatersprite.
NIXIEWater sprite.
NIXIEUndeliverable piece of mail: Slang.
NIXIEFemale sprite
NIXIEUndeliverable piece of mail
NIXIEUndeliverable letter, in post-office talk
NIXIEDead letter, in post office talk
NIXIEWater sprite
NIXIEGermanic water spirit
NIXIEUndeliverable letter, to a postal worker