headless

Short definition from Wiktionary

Adjective

1. 1
   Without a head (body part): Synonym of decapitated.
2. 2
   Without a head (body part): Naturally having and needing no head.
3. 3
   Without a head (hardware or device feature).
4. 4
   Without leadership.
5. 5
   Not having a head morpheme or word.
6. 6
   Running without a graphical user interface; running without any attached output device (e.g., monitor) or input device (e.g., keyboard, mouse).
7. 7
   Without a head of foam.
8. 8
   Heedless.
9. 9
   Rimless, not having a cartridge case rim (flange).