A venerable elderly man, a man respected for his long experience; specifically (a journalistic name for) any of several distinguished British politicians, especially (chiefly with the) William Ewart Gladstone, British Prime Minister four times between 1868 and 1894 (abbreviated G.O.M.).
Origin
Mid 19th century.
Definition of grand old man in US English:
grand old man
noun
A venerable elderly man, a man respected for his long experience; specifically (a journalistic name for) any of several distinguished British politicians, especially (chiefly with the) William Ewart Gladstone, British Prime Minister four times between 1868 and 1894 (abbreviated G.O.M.).