Definition of "ceil"

It is nearly always old and bare, built of rough boards, and neither plastered nor ceiled.

1903 June 1, W[illiam] E[dward] Burghardt Du Bois, “Of the Quest of the Golden Fleece”, in The Souls of Black Folk: Essays and Sketches, 2nd edition, Chicago, Ill.: A[lexander] C[aldwell] McClurg & Co., page 139

[…] The mossy sward / Beneath their feet, their carpet was, / An azure ceil, the sky above; […]

1890, Ambrose E. Pratt, Two Hundred and Fiftieth Anniversary Celebration of Sandwich and Bourne, at Sandwich, Massachusetts, September 3, 1889, page 89