What it is: A sustained competition between two or more states, each trying to outdo the other in the quantity and power of the weapons they possess.
What it means: The states involved see this as a means of defence, regardless of the appalling risks. The risks are made greater by the use of bluff, counter-bluff and unscrupulous spying techniques. The most famous example of an arms race occurred during the Cold War, in which the USA and the USSR competed to own the greatest supply of nuclear weapons.
Think about it: Think about the risks involved in any kind of dangerous competition - and especially the risks to people not actually competing but caught up in the violence.