Postprandial means after eating a meal while preprandial is before a meal.
This term is used in many contexts. In an upper class Victorian household a postprandial glass of port or brandy and cigar was enjoyed by the gentlemen while the ladies had a postprandial coffee.
Nowadays it is more oftent to be found in relation to blood sugar (or blood glucose) levels, which are normally measured 2 hours after and before eating in a postprandial glucose test.