The term 'longish skirt' can be summarized by the crossword solution MIDI, which is a four-letter word. MIDI is an acronym for Musical Instrument Digital Interface, which is a technical standard that allows electronic musical instruments and computers to communicate with each other. A MIDI skirt is a type of skirt that falls between a mini and a maxi skirt in terms of length, usually ending just above the knee. It is a popular style of skirt for women, as it is both fashionable and comfortable.