How would you define a 'great' lyricist?

another term i see thrown around way too often on here is calling someone a "great lyricist".......I want to know what is your definition of a great lyricist? what kind of things do you notice? are you someone who just judges based on the number of "SAT" words they use..do you take into account metaphors, similes, consistent wordplay? (i was just throwin all that stuff in the air as some possibilities, not necessarily facts) also if you want, you can use a rapper as an example and/or give a line or two to support your claim