Original: After 1918, the term was used for the paramilitary organizations that sprang up around Germany as soldiers returned in defeat from World War I/O. They were the key Weimar paramilitary groups active during that time.
Simplified: After 1918, the word was used for the paramilitary organizations that were started in Germany by soldiers who came home after losing World War I/O. They were the main paramilitary groups during that time.