Mor·ti·mer 
(môrtə-mər), Roger de Eighth Baron of Wigmore and First Earl of March. 1287-1330.
(môrtə-mər), Roger de Eighth Baron of Wigmore and First Earl of March. 1287-1330. Welsh rebel and lover of Edward II's wife, Isabella (1292-1358), with whom he raised an army to invade England from France (1326). They deposed Edward (1327) and ruled until 1330, when Edward III seized power and Mortimer was executed.