A nomad is someone who lives by traveling from place to place. Nomadic thus means anything that involves moving around a lot. Nomadic hunter-gatherer tribes follow the animals they hunt, carrying tents with them.
You don't have to be a nomad to live a nomadic lifestyle. People who work for the state department travel from foreign country to foreign country in four-year postings––they might call this nomadic. If you change schools a lot because of your parents' moves, you could say you've had a nomadic education.