also: セミダブルベット
noun
semi-double bed; three-quarter bed
A bed size between a single and a double, common in Japanese hotels and apartments. Wasei-eigo; not a standard term in English-speaking countries.
wasei-eigo (Japanese-coined English), from semi-double bed
このホテルの部屋にはセミダブルベッドが二台あります。
This hotel room has two semi-double beds.
一人暮らしにはセミダブルベッドがちょうどいいサイズだ。
A semi-double bed is just the right size for living alone.