Basically it is just the word "interesting" but with the addition of "mar" in between the inter and esting. So by adding "mar" you receive the word "intermaresting". Also a good way to start an awkward conversation or break the ice when the other person realises you didn't say "interesting", but instead "intermaresting".
Guy # 1. Cool story bro, ya know it was really intermaresting...
Guy # 2. Thanks browskie, weird way to say interesting though man.
Guy # 1. Its a new thing, you should try it out sometime.
Guy # 2. Yeah dude, I will!