The only two hits I can find searching for "textureless_map" on the MathWorks website are this Answers post and this other Answers post you wrote yesterday. In that other post, textureless_map was the name of a variable.
What does the data it contains represent? Why do you need to work with that specific data? Those are questions you're going to need to ask the person from whom you received the code in the other post that uses it.
