noun

• The overhead closure of a room.
• The upper limit of an object or action.
• (aviation) The highest altitude at which an aircraft can safely maintain flight.
• (meteorology) The measurement of visible distance from ground or sea level to an overcast cloud cover; under a clear sky, the ceiling measurement is identified as "unlimited."
• (mathematics) The smallest integer greater than or equal to a given number.
• (nautical) The inner planking of a vessel.
• (finance) The maximum permitted level in a financial transaction.
• (architecture) The overhead interior surface that covers the upper limits of a room.