Other forms: fillings
Food is filling when a small amount leaves you full. Porridge is filling, a bowl of soup with bread is filling, three slices of cucumber are not.
The noun is everywhere too: the filling is whatever goes inside — the cream in a doughnut, the cheese in a sandwich, the meat in a pie. At the dentist a filling is the hard material packed into a drilled tooth, and 'I need a filling' is a sentence you will hear in any waiting room. Cushions and duvets have a filling as well, the soft stuff inside. Keep filling apart from fulfilling: a meal is filling, a job is fulfilling. And a filling station is where you fill the car with petrol.
1adjectivefillingOf food: making you feel full quickly.
“The stew was cheap and surprisingly filling.”
synonyms: substantial, satisfying
2nounpieThe food put inside a pie, sandwich, cake or similar.
“The filling was hot but the pastry was still cold.”
3nounhardThe hard material a dentist puts into a hole in a tooth.
“She needed two fillings after the check-up.”
4nounsoftSoft material used to fill the inside of something.
“The cushions have a synthetic filling that flattens quickly.”
Too few real examples of this word to estimate which sense is commonest.