n, pl  -trae   1  :  a small anatomical opening (as in a bone): as  a  :  OVAL WINDOW  b  :  ROUND WINDOW  2 a  :  an opening like a window cut in bone (as in the inner ear in the fenestration operation)  b  :  a window cut in a surgical instrument (as an endoscope) fe*nes*tral adj 
 
 
 
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