What do we mean by “poetic language”?

Answers I’ve gotten from first-year students over the years:
 
Language that rhymes
Language that has rhythm (meter)
Old-fashioned language written the way people used to speak a long time ago
Old-fashioned language, with a lot of “thees” and “thous” and “lests” and “dosts” in it
Language that has a lot of metaphors in it
Language that is beautiful
Language that is more beautiful than meaningful
Language that is unusually moving
Language I don’t understand (can’t be bothered with, that annoys me, and so on)