arduous /ärˈdū-əs/

1. Steep, difficult to climb
2. Difficult to accomplish
3. Laborious

• cesiums
• cespitose
• cess
• cessation
• cessations
• cesse
• cessed
• cesser
• cessers
• cesses
• cessing
• cessio
• cession
• cessionaries
• cessionary
• cessions
• cesspit
• cesspits
• cesspool
• cesspools
• cesti
• c'est la vie
• Cestoda
• cestode
• cestodes