The owner's manual for my 2003 lx says I have a "manual overdrive transmission." What is it and how does overdrive work in a manual... or did someone print something wrong?

 

fifth gear is an "overdrive" ratio

 

What's the difference between that and a normal fifth gear?

 

No difference. Fifth gear is just called overdrive because the gear ratio is less than 1. All other gears have ratios >1, so it takes more than 1 revolution of the engine to rotate the crankshaft once (??? uhh i've no idea what the term is). In fifth gear, it takes less than one revolution of the engine to rotate the crankshaft once, hence the "over"drive (whereas the fourth gear is more like "drive" and all others are more like "under"drive)

 

Thats a pretty good explanation.
though 4th gear, assuming its 1:1 would be called "direct drive"