anarthrous

from The Collaborative International Dictionary of English v.0.48

Anarthrous \An*ar"throus\, a. [Gr. 'a`narqros without joints,
   without the article; 'an priv. + 'a`rqron joint, the
   article.]
   1. (Gr. Gram.) Used without the article; as, an anarthrous
      substantive.
      [1913 Webster]

   2. (Zool.) Without joints, or having the joints indistinct,
      as some insects.
      [1913 Webster]