If you actually conducted research in it then yes it would be research. I don't see a need to label it any differently. And this may sound crazy, so someone can correct me if I'm totally wrong, but I'm not sure if it's even necessary to mention that it was cut short.
You obviously did enough work to get a poster presentation out of it which means you made enough scientific observations to draw conclusions-- It's not like you worked on it for a week and called it quits. You have something to show for it.
If an adcom asked you about it, you could simply present the findings that were in the poster presentation and end it there. I've never done research in a single project and saw it through completely from beginning to end because the research I did were 2+ year projects and I was only assigned to assist with one portion of it. I did enough research however, to draw reasonable conclusions worthy of a presentation though. I find it unlikely you would be penalized for that.