1. Designed to be durable for heavy use or extreme conditions; industrial strength. My pickup has a heavy-duty lining to protect it from all the stuff I load in it. If you're hiking that mountain, you'll need some heavy-duty boots.

2. By extension, very serious; extreme. The media has been devoting some pretty heavy-duty coverage to the trial. He's been in trouble before, but nothing like this. This is heavy-duty. Wow, those are some heavy-duty doughnuts you've got there. They're as big as my head!