n 1  :  an arc of 90° that is one quarter of a circle  2  :  any of the four more or less equivalent segments into which an anatomic structure may be divided by vertical and horizontal partitioning through its midpoint <pain in the lower right of the abdomen>  <the left upper of the retina>  .
 
 
 
Similar sounding terms:  cau·ter·ant 
 
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