por ‧ ridge /ˈpɒrɪdʒ $ ˈpɑː-, ˈpɔː-/ BrE AmE noun [uncountable]
[ Date: 1500-1600 ; Origin: pottage 'soup' (12-20 centuries) , from Old French potage , from pot 'pot' ]
1 . ↑ oats that are cooked with milk or water and served hot for breakfast SYN oatmeal American English
2 . British English informal a period of time spent in prison
do porridge (=spend time in prison)