1. Headless.
2. <marine biology> Without a distinct head; a term applied to bivalve mollusks.
3. <botany> Having the style spring from the base, instead of from the apex, as is the case in certain ovaries.
4. Without a leader or chief.
5. Wanting the beginning. "A false or acephalous structure of sentence." (De Quincey)
6. Deficient and the beginning, as a line of poetry.
See: Acephal.