What is tight little ass?

The phrase "tight little ass" is informal and generally considered slang. It can be used in a variety of contexts, often related to describing physical attributes, but it can also be objectifying or offensive depending on the context or audience. It's important to consider the appropriateness and sensitivity of using such language, as it may not be suitable in all settings. If you have a specific context or usage in mind, please feel free to share more details for a more tailored response.