The smallest integer ⎾x⏋not less than a given real number x. So ⎾3.2⏋ = 4 and ⎾5⏋ = 5. Comparefloor.
Computer
If x is a real number, then ceiling(x), also written as ⌈x⌉, is the smallest integer greater than or equal to x.
Economics
In trade cycle theory this is the maximum level of aggregate real output the economy can attain during the expansion, which corresponds to full employment. See alsofloor.