Mostly; very nearly. We're pretty much finished—just a few last-minute tweaks to the code. Support for the bill has been pretty much unanimous in the House of Representatives.
Almost, nearly, approximately, as in Our homework was pretty much finished. This adverbial usage differs from the use of pretty for "considerable" (as in pretty penny). [c. 1800]
pretty ˈmuch/ˈwell(British English also pretty ˈnearly) (American English also pretty ˈnear) (spoken) almost; just about: This nightclub is pretty much the best this town can offer. ♢ I’m pretty well disgusted by your behaviour. ♢ It’s worth pretty near a thousand dollars.
For the most part; mostly: "The ... matter was pretty much dying down" (John Strahinich).