Is it ensure, insure, or assure?
/mis-fee'chr/ or /mis'fee"chr/ A feature that eventually causes lossage, possibly because it is not adequate for a new situation that has evolved. Since it results from a deliberate and properly implemented feature, a misfeature is not a bug. Nor is it a simple unforeseen side effect; the term implies that the feature in question was carefully planned, but its long-term consequences were not accurately or adequately predicted (which is quite different from not having thought ahead at all). A misfeature can be a particularly stubborn problem to resolve, because fixing it usually involves a substantial philosophical change to the structure of the system involved.
Many misfeatures (especially in user-interface design) arise because the designers/implementors mistake their personal tastes for laws of nature. Often a former feature becomes a misfeature because trade-offs were made whose parameters subsequently change (possibly only in the judgment of the implementors). "Well, yeah, it is kind of a misfeature that file names are limited to six characters, but the original implementors wanted to save directory space and we"re stuck with it for now."