When city idiots fire guns into the air at midnight on New Year's Eve, with the rounds landing indiscriminately somewhere else, they've performed an act of indirect fire.
Here's a 107mm rocket set up that is fairly common and simplistic in design. The bad guys line these up in a row by the dozens if they can get away with it. For scale, these rockets are about the size of a household fire extinguisher that would be found under a sink or mounted on the wall. I believe they sport about 2 lbs of TNT like explosive. KAPOW! If they hit compacted gravel, they'll blow a hole in the ground from a few inches to about a foot deep. Gravel will be blown away from about the size of a dinner plate to the size of a pizza pan. There's about a gazillion of them out there.
( ref: wiki ) Indirect fire is most commonly associated with field artillery. It is also used with mortars and naval guns against shore targets, sometimes with machine guns and has been used with tank and anti-tank guns and by anti-aircraft guns against surface targets.