/mis-fē-chər/
n. A feature that eventually causes lossage, possibly because it is not adequate for a new situation which has evolved. It is not the same as a bug, because fixing it involves a substantial philosophical change to the structure of the system involved. A misfeature is different from a simple unforeseen side effect; the term implies that the misfeature was actually carefully planned to be that way, but its future consequences or circumstances just weren't predicted accurately. This is different from just not having thought ahead about it at all. Many misfeatures (especially in user-interface design) arise because the designers/implementors mistook their personal tastes for laws of nature. Often a former feature becomes a misfeature because a tradeoff was made whose parameters subsequently changed (possibly only in the judgment of the implementors).
"Well, yeah, it is kind of a misfeature that file names are limited to 6 characters, but the original implementors wanted to save directory space and we're stuck with it for now."