A person who plants a bomb that results in at least one homicide.
This generic term can also identify the method used to deliver the bomb. For example, a "suicide bomber" (the phrase that "homicide bomber" was invented to displace) delivers the bomb by killing himself or herself while killing others. Another example is a "mail bomber," who sends his or her murderous bomb by mail, like the Unabomber Ted Kaczynski.
Both of these are different from a more generic "homicide bomber" who personally plants a bomb with the intent “only” to commit homicide, and not suicide.
There are many suicide bombers in the Middle East, but Timothy McVeigh was a homicide bomber.