horseshoe moustache UK /ˈhɔːs.ʃuː məsˈtɑːʃ/US /ˈhɔːɹs.ʃuː ˈmʌstæʃ/ noun1 •A moustache covering the lip and having vertical extensions reaching down from the corners of the lips to the jawline, resembling an upside-down U or a horseshoe. formshorseshoe moustaches