A rebellion is when you rise up and fight those in power, usually on a large scale. In "Star Wars," the good guys fighting the powerful, evil empire were known as the rebellion.
If you know that a rebel is someone who fights authority, then you won’t be surprised that a rebellion is something similar. Rebellions can be wars, particularly wars for independence from the ruling government, but many rebellions never come to armed conflict. Most of the time they're wars of words, or even just small-scale rule-breaking that is supposed to make a larger point. Students might wear shorts to school, for example, as a rebellion against the dress code.
n organized opposition to authority; a conflict in which one faction tries to wrest control from another
a widespread rebellion in 1381 against poll taxes and other inequities that oppressed the poorer people of England; suppressed by Richard II
discontent with British administration in India led to numerous mutinies in 1857 and 1858; the revolt was put down after several battles and sieges (notably the siege at Lucknow)
an organized rebellion aimed at overthrowing a constituted government through the use of subversion and armed conflict
an uprising by Palestinian Arabs (in both the Gaza Strip and the West Bank) against Israel in the late 1980s and again in 2000
open rebellion against constituted authority (especially by seamen or soldiers against their officers)