" arduous "

1: requiring considerable physical or mental effort;

  * e.g., " ... climbing Mount Everest is an arduous, exhausting challenge "

•  Synonyms : 

•  Augean,

•  backbreaking,

•  challenging,

•  demanding,

•  difficult,

•  effortful,

•  exacting,

•  formidable,

•  grueling,

•  hard,

•  heavy,

•  hellacious,

•  herculean,

•  killer,

•  laborious,

•  moiling,

•  murderous,

•  pick-and-shovel,

•  rigorous,

•  rough,

•  rugged,

•  severe,

•  stiff,

•  strenuous,

•  sweaty,

•  tall,

•  testing,

•  toilsome,

•  tough,

•  uphill

•  Antonyms : 

•  cheap,

•  easy,

•  effortless,

•  facile,

•  light,

•  mindless,

•  simple,

•  soft,

•  undemanding

2: requiring much time, effort, or careful attention;

  * e.g., " ... the arduous task of doing the research for my term paper "

•  Synonyms : 

•  burdensome,

•  challenging,

•  demanding,

•  exacting,

•  grueling,

•  killing,

•  laborious,

•  onerous,

•  persnickety,

•  taxing,

•  toilsome

•  Antonyms : 

•  light,

•  nondemanding,

•  unchallenging,

•  undemanding