This word is overused to mean many things: "attractive," "graceful," "pleasing," "delicate," "comely," "fair," and "lovely." It is also overused to mean "moderately," "somewhat," or "to a degree" (pretty tired, pretty lucky). Slangy or trite phrases to avoid include "sitting pretty," "pretty up," "a pretty penny," and "pretty much."
Dictionary of problem words and expressions. Harry Shaw. 1975.