Without a head, or acting without thought or planning; behaving foolishly or without leadership.
Compound of 'head' and the suffix '-less' (meaning 'without'). Old English 'heafdleas' shows this word has been in use for over a thousand years, originally describing literally decapitated bodies.
The phrase 'running around like a headless chicken' comes from a real 1940s phenomenon—a chicken named Mike survived five months after decapitation, spawning tours and the phrase we still use to describe panic, all from actual neurology!
Complete word intelligence in one call. Free tier — 50 lookups/day.