Dictionary.com gives us a few useful definitions for "overwrite":
1.to write in too elaborate, burdensome, diffuse, or prolix a style: He overwrites his essays to the point of absurdity.
2.to write in excess of the requirements, esp. so as to defeat the original intention: That young playwright tends to overwrite her big scenes.
From these definitions, let's break down the key terms.
Overwritten fiction is...
too elaborate--its tone and voice don't fit the characters and situation.
burdensome--it is dense and difficult to understand.
diffuse--it goes on tangents, lacks focus.
prolix--it rambles and it explains more than it needs too.
exceeds the requirements, defeating the purpose--it uses the same effect repeatedly in a scene, sucking away power.
In an upcoming series of posts, I'll examine examples of each of these overwriting "sins" so you can identify them in your own work, then discuss solutions.
Are there other frequently-used critique terms that confuse you?