Webster's Revised Unabridged Dictionary · 1913

Anarthrous

Anarthrous ({not transcribed}) , adjective

[Greek 'a`narqros without joints, without the article; 'an priv. + 'a`rqron joint, the article.]

1.
(Greek Grammar) Used without the article; as, an anarthrous substantive.
2.
(Zoology) Without joints, or having the joints indistinct, as some insects.