The definition of arduous is a way of describing something that is extremely tiring and difficult.(adjective)
The John Beargrease Sled Dog Marathon is an example of an arduous race.
Arduous is defined as a sharp, high climb where reaching the top is a challenge.(adjective)
Mt. Everest is an example of an arduous incline.
See arduous in Webster's New World College Dictionary
Origin: L arduus, steep < IE *er(ə)dh-, high, to grow (> L arbor, tree) < base *er-, to set in motion, run
See arduous in American Heritage Dictionary 4
Origin: From Latin arduus, high, steep.
Learn more about arduous