Mealie meal is a relatively coarse flour (much coarser than cornflour or cornstarch) made from maize. It is a staple food in many parts of sub-Saharan Africa.
Add to boiling water, or boiling milk for a creamier texture, and the result is a porridge with a very thick texture. It is eaten at breakfast as porridge, or with meat and gravy as a mashed-potato substitute. It's similar to Italian polenta or American grits except it's usually made of a white rather than a yellow maize variety.