Definition of: arduous

(är′joo·əs) adjective
1. Involving great labor, hardship, or difficulty; difficult.
2. Toiling strenuously; energetic.
3. Steep; hard to climb or surmount. [<L arduus steep]
—ar′·du·ous·ly adverb
—ar′du·ous·ness noun Synonyms: difficult, exhausting, hard, laborious, onerous, severe, toilsome, trying. Hard may be active or passive; a thing may be hard to do or hard to bear. Arduous is always active. That which is difficult may require labor, or simply skill and address, as a difficult problem or puzzle. That which is arduous always requires persevering toil. Antonyms: easy, facile, light, pleasant, slight, trifling, trivial.