Definition of "casement"

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, The Holy Bible, […] (King James Version), London: […] Robert Barker, […], Proverbs 7:6–7

Passing through Tokenhouse Yard, in Lothbury, of a sudden a casement violently opened just over my head, and a woman gave three frightful screeches, and then cried, ‘Oh! death, death, death!’ in a most inimitable tone, and which struck me with horror and a chillness in my very blood.

1722, Daniel Defoe, A Journal of the Plague Year

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, L[etitia] E[lizabeth] L[andon], chapter XXI, in Francesca Carrara. […], volume II, London: Richard Bentley, […], (successor to Henry Colburn), page 229

The street-lamps always burn; but scarce a casement / In house or palace front from roof to basement / Doth glow or gleam athwart the mirk air cast.

1873, James Thomson (B.V.), The City of Dreadful Night

The house was a big elaborate limestone affair, evidently new. Winter sunshine sparkled on lace-hung casement, on glass marquise, and the burnished bronze foliations of grille and door.

1907 August, Robert W[illiam] Chambers, chapter I, in The Younger Set, New York, N.Y.: D. Appleton & Company