Sagittal

adj. resembling an arrow or arrowhead; pertaining to an arrow or arrowhead

In sciences dealing with the anatomy of animals, precise anatomical terms of location are necessary for a variety of reasons. Non-scientists often wonder why zoological and human anatomists use complex terminology to describe locations on a body, when common terms like "up", "down", "top" and "bottom" could be used instead.
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Adjective
1. located in a plane that is parallel to the central plane of the sagittal suture
(similar) mesial

adj. sagittal, resembling an arrow or arrowhead

(a.)
Of or pertaining to the sagittal suture; in the region of the sagittal suture; rabdoidal; as, the sagittal furrow, or groove, on the inner surface of the roof of the skull.
  

(a.)
Of or pertaining to an arrow; resembling an arrow; furnished with an arrowlike appendage.
  

(a.)
In the mesial plane; mesial; as, a sagittal section of an animal.