1) Muscle of the torso 
The longissimus is the muscle lateral to the semispinalis. It is the longest subdivision of the sacrospinalis that extends forward into the transverse processes of the posterior cervical vertebrae. ==Structure== ===Longissimus thoracis=== The longissimus thoracis is the intermediate and largest of the continuations of the sacrospinalis. In the lum...
(lon-jis´ĭ-mәs) Latin word meaning longest; a term used in anatomy.
(muscle) Type: Term Definitions: 1. the intermediate division of the erector spinae muscle having three subdivisions: longissimus capitis muscle, longissimus cervicis muscle, and longissimus thoracis muscle. Synonyms: musculus longissimus
superlative of Latin longus = long, hence, the longest.