The Great Gatsby, to look purposeless

Could you please tell me the meaning of "purposeless" in the following excerpt from the chapter 3 of The Great Gatsby?

As soon as I arrived I made an attempt to find my host but the two or three people of whom I asked his whereabouts stared at me in such an amazed way and denied so vehemently any knowledge of his movements that I slunk off in the direction of the cocktail table—the only place in the garden where a single man could linger without looking purposeless and alone.

Thank you.