Something that's rasping has a harsh, scratchy sound. If your old car's rasping engine gets even louder, you might want to take it to a mechanic.
You'll most often find the adjective rasping describing someone's voice: "His rasping singing voice accompanied the choir," or "I was so thirsty after the hike that i could only make a dry, rasping sound when I tried to talk." To rasp means to scrape, from the Old French verb rasper, or "to grate."