Longman Dictionary of Contemporary English - mono

~1 n informal 1 AmE an infectious illness that makes your lymph glands swell and makes you feel weak and tired for a long time afterwards; glandular fever BrE 2 a system of recording or broadcasting sound, in which the sound comes from only one direction  (- compare stereo1) ~2 adj using a system of recording or broadcasting sound in which all the sound comes from only one direction  (a mono recording)  (- compare stereo2)