Definition of "acidulous"

acidulous

/əˈsɪdjʊləs/

adjective
1. Slightly sour; sub-acid; sourish.
  Quotations
  the hard, acidulous, metallic tincture of the spring
  1796, Edmund Burke, A Letter from the Right Honourable Edmund Burke to a Noble Lord, on the Attacks Made upon Him and His Pension
2. (figurative) Sharp; caustic.
  Quotations
  He talked with acidulous tolerance of the exalted personages who had sent Ashenden to X.
  1931, William Somerset Maugham, His Excellency
3. Containing carbonic acid.