ceil·ing / ˈsēling/ • n. 1. the upper interior surface of a room or other similar compartment. ∎ fig. an upper limit, typically one set on prices, wages, or expenditure.See also glass ceiling. ∎  the maximum altitude that a particular aircraft can reach. ∎  the altitude of the base of a cloud layer.2. the inside planking of a ship's bottom and sides.

ceiling †lining of the inside of roof or walls XIV; †screen of tapestry, curtain XV; (naut.) inside planking of a ship's bottom XVII; plaster covering the top of a room XVI. Late ME. celynge, siling, early modEng. syll-, seel-, ciel-, seyl-, appearing contemp. with celure, selure, sil(l)our, later seller canopy, hangings, tapestry (XIV–XVI); these corresp. in use to medL. cēlum (XII) cēlātūra (XIII), cēlūra (XIV), but the meaning is freq. uncert.; possible OF. connections are rare, and it remains doubtful whether L., cælum heaven is the ult. base and how far L. cælāre engrave, cælātūra engraving, carving are concerned.

ceiling If x is a real number, then ceiling(x), also written as ⌈x⌉, is the smallest integer greater than or equal to x.