What does the phrase one s ego at mean?

The phrase "one's ego at" is incomplete and doesn't make sense on its own. It needs more context to understand its meaning.

It's likely you are thinking of a phrase like:

* "One's ego is at stake" - This means that a person's sense of self-worth or importance is threatened. For example, someone might say "My ego is at stake if I lose this competition" meaning they would feel bad about themselves if they lost.

* "One's ego is at play" - This means that a person's pride or sense of self-importance is influencing their actions or decisions. For example, someone might say "Their ego is at play in this situation" meaning they are more concerned with how they appear than with what is best for everyone.

Please provide more context or the full phrase you're trying to understand, and I can give you a more accurate explanation.