Other forms: meaninglessly
If something's meaningless, it has no real value, purpose, or significance. If someone repeatedly hurts your feelings and casually says they're sorry, you might feel like the apology is meaningless.
Words in a book will be meaningless to you if they're written in a language you don't understand, and the small talk you engage in when you run into an acquaintance at the supermarket is often meaningless too. You can probably think of rules that don't have any good reason behind them, and these are also meaningless. When something is important to you, it has meaning — and when it's not, it's meaningless.