Cut off and ceiling are two very different words. 1. "Cut off" means a designated limit of something or it can also mean an act to try and stop something. For example: This year's cut off percentage is 80%. (designated limit) To cut someone off when they are speaking is considered as rude. (trying to stop or interrupt) Whereas "Ceiling" means either the upper interior surface of the room or an upper limit set on anything like expenses, wages, prices, etc For example: The ceiling was very high. (upper interior of a room) The world authorities should impose a ceiling on carbon emissions. (upper limit) I hope this helps.

It's a good question because I would say that the words are sometimes synonymous, but not always. Oxford's first example sentence is: https://en.oxforddictionaries.com/definition/cut-off ‘2,500 g is the standard cut-off below which infants are categorized as ‘low birthweight’’ It indicates the upper limit or threshold for the purposes of classification or eligibility. You see "cut-off (n)" or "cut-off point/date etc." used in a similar way also in the area of tax. A person may be eligible for a particular tax credit or allowance e.g. provided that their income does not exceed a specific amount ("cut-off point") or provided that they apply by a certain deadline ("cut-off date"). You if you fall on the right side of a "cut-off", you are eligible for something and vice versa. On the other hand "ceiling" is used more in contexts like progress or maximum capacity. So the "glass ceiling" is the invisible limit beyond which a certain named group of people such as women cannot progress. A "contributions ceiling" is the maximum amount that someone can contribute. An "emissions ceiling" could be the maximum limit beyond which a coal plant or a nation should not emit smoke from fossil fuels.