There is shared understanding of what 'morality' means. There is also disagreement. The same can be said of a wide variety of other words, such as 'christianity

There is shared understanding of what 'morality' means. There is also disagreement. The same can be said of a wide variety of other words, such as 'christianity', 'freedom', or 'liberal'. None of these words are meaningless or useless in conversation despite the existence of some disagreement about their meanings.