What does "monosaccharid" mean?

Monosaccharid: A simple sugar; any of a number of sugars (including the trioses, tetroses, pentoses, hexoses, etc.), not decomposable into simpler sugars by hydrolysis. Specif., as used by some, a hexose. The monosaccharides are all open-chain compounds containing hydroxyl groups and either an aldehyde group or a ketone group.