Real Dictionary

sage
adjective: Sage means wise and knowledgeable, especially as the result of a lot of experience.
countable noun: A sage is a person who is regarded as being very wise.

Sage in American English
Russell1816-1906; U.S. financier

sage in American English 1
wise, discerning, judicious, etc.
adjective: wise, judicious, or prudent
noun: a profoundly wise person; a person famed for wisdom

sage in American English 2
any of a genus (Salvia) of plants of the mint family, having a two-lipped corolla and two stamens: sages are cultivated for ornament, as the scarlet sage (S. splendens) with brilliant red flowers, or for flavoring, as the garden sage (S. officinalis) with
noun: any plant or shrub belonging to the genus Salvia, of the mint family

SAGE in British English
noun acronym for: Scientific Advisory Group for Emergencies

sage in British English 1
adjective: profoundly wise or prudent
noun: a man revered for his profound wisdom

sage in British English 2
noun: a perennial Mediterranean plant, Salvia officinalis, having grey-green leaves and purple, blue, or white flowers: family Lamiaceae (labiates)