casement

noun3

1. •
   A window sash that is hinged on the side.

   • For at the window of my house I looked through my casement, and beheld among the simple ones, I discerned among the youths, a young man void of understanding. — 1611
2. •
   A window having such sashes; a casement window.ᵂᵖ

   • Some slight noise had awakened Francesca, and opening her casement, she looked through the thick and misty air, and saw him riding slowly over the heath. — 1834
3. •
   A casemate. Some writers and readers consider casement a catachresis when used in this sense.