"Close enough for jazz"

This expression is from musicians tuning their instruments, but not being too particular about it. The inference is that since jazz musicians "bend" the note much of the time, anyway, the tuning of the instrument is not of paramount importance. There is, however, the implication that jazz is a sub-par type of music, and some jazzers resent the expression. Be that as it may, it has come to have a broader meaning: "It is adequate, and there is no need to go to great lengths to make it better."