Dictionary:

acephalous

  (ā-sĕf'ə-ləs)

1. Biology. Headless or lacking a clearly defined head: acephalous worms.
2. Having no leader.

[From Medieval Latin acephalus, from Greek akephalos : a-, without; see a–¹ + kephalē, head; see –cephalous.]

acephalous [a‐sef‐ăl‐ŭs], the Greek word for ‘headless’, applied to a metrical verse line that lacks the first syllable expected according to regular metre; e.g. an iambic pentameter missing the first unstressed syllable, as sometimes in Chaucer:

Twenty bookès, clad in blak or reed

Noun: acephalexis.

adj.

In the surprising condition of the Crusader who absently pulled at his forelock some hours after a Saracen scimitar had, unconsciously to him, passed through his neck, as related by de Joinville.

The adjective has one meaning:

Meaning #1: (biology) lacking a head or a clearly defined head