Pretending to be well-educated when he was not. Greene called him an "upstart crow".
A guy called Greene did, in a book called Greene's Groatsworth of Wit. Although some people think that Greene did not actually write that book, and the remarks about Shakespeare are not actually a diss.
Some speculate that he did because of Greene's colorful personality.
Robert Greene accused him of being an "upstart crow" because he dared to write plays when he wasn't a university man. It didn't seem to matter much to anyone else.
Nobody called Shakespeare an "upset crow". Robert Greene, in a pamphlet called "Greene's Groatsworth of Wit" called him an "upstart crow". Why? Because Greene was a university man and he looked down at Shakespeare, who only had a grammar school education, as uneducated. He was therefore an upstart to pretend that he could write as well as people who had been to university. Of course Greene was full of it. Shakespeare was a much better writer than Greene himself. I'm not sure why he called him a crow. Maybe it was because Shakespeare had black hair, as the Chandos portrait shows.
Robert Greene
People like Robert Greene, for example, were jealous of Shakespeare's talent and success.
Greene apparently resented the fact that Shakespeare was writing plays and getting them performed while Greene was starving to death, especially since Greene was better-educated. But some people think that the pamphlet in which these sentiments are expressed were not really written by Greene at all, and others think that they are misinterpreted as a kind of nasty criticism.
Robert Greene in his pamphlet Greene's Groatsworth of Wit, published in 1592.
Impeach
Suiting.
Robert Greene
1592, by Robert Greene.