Definition of arduous adjective from the Oxford Advanced Learner's Dictionary

 

arduous

 adjective
adjective
BrE BrE//ˈɑːdjuəs//
 
, BrE//ˈɑːdʒuəs//
 
; NAmE NAmE//ˈɑːrdʒuəs//
 
Describing work
 
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involving a lot of effort and energy, especially over a period of time an arduous journey across the Andes The work was arduous. See related entries: Describing work Word Origin mid 16th cent.: from Latin arduus ‘steep, difficult’ + -ous.Extra examples It was physically arduous work. She was now faced with an arduous trek across the mountains. The road back to political stability is long and arduous. an arduous task/​process
See the Oxford Advanced American Dictionary entry: arduous