Hundred/ˈhʌndrəd/ Definition 1 of 4Pro Tip 1/3Round Numbers Hundred is often used to estimate or round numbers for simplicity. There were roughly a hundred people at the event. Pro Tip 2/3Not Always Exact 'Hundred' can be used to imply many, without meaning the exact number. I have hundreds of photos in my album. Pro Tip 3/3Idiomatic Expressions 'Hundred' is used in expressions like 'give it one hundred percent', meaning all-out effort. You need to give it one hundred percent to succeed.