Toothless means lacking teeth, or more commonly, lacking the power to enforce rules or achieve results.

When something is literally toothless, it has no teeth. A newborn baby is toothless until those first teeth come in. An elderly person might become toothless if they lose their teeth over time. But the word's more interesting meaning is metaphorical.

A toothless law sounds tough but can't actually punish anyone who breaks it. Imagine a school rule against running in the hallways, but there's no consequence for running: that rule is toothless. A toothless threat is one nobody takes seriously because the person making it won't or can't follow through. If your little sister warns she'll tell on you for something, but she does this every day and never actually tells, her threats become toothless.

The metaphor comes from how teeth give animals their bite: a lion without teeth can roar impressively, but it can't hunt effectively. Similarly, a toothless committee, regulation, or agreement might exist on paper but accomplish nothing in practice. When people call something toothless, they mean it looks official or sounds serious but has no real force behind it.