Definition of "monotonous"

monotonous

/məˈnɒtənəs/

adjective
comparative more monotonous, superlative most monotonous
1. Having an unvarying pitch or tone.
  Quotations
  "But my daughter—but the Lady Eveline"—said the Fleming, with some slight change in his monotonous voice, which seemed to express doubt and perplexity—"You are cruel conquerors, and—"
  1825 June 22, [Walter Scott], chapter V, in Tales of the Crusaders. […], volume I (The Betrothed), Edinburgh: […] [James Ballantyne and Co.] for Archibald Constable and Co.; London: Hurst, Robinson, and Co., page 95
2. Tedious, repetitious, or lacking in variety.
  Quotations
  [L]istening for a moment, she heard the monotonous and heavy tread of the soldier echoing through the passage.
  1834, L[etitia] E[lizabeth] L[andon], chapter VII, in Francesca Carrara. […], volume III, London: Richard Bentley, […], (successor to Henry Colburn), page 49