laborious
adj.describing a task that is very tiring, difficult, or takes a long time to finish. You use this when something requires a lot of hard work.
adj.requiring great physical or mental effort; tedious and exhausting. Often used to describe processes that are slow or involve repetitive, difficult tasks.
“The manual data entry was a laborious task.”
“The researchers spent several months on a laborious process of cross-referencing every single document in the archive.”
“While the initial concept was simple, the execution proved laborious, requiring the team to manually verify thousands of data points before the final report could be published.”
“If something new is found, the species will be described scientifically and given a name—a laborious process that can often take a couple of years.”
“Instead of toiling through trial and error, scientists can let the machine run through laborious processes in its virtual environment, leaving the human to do the final checks and connect the dots.”
From Old French laborios, from Latin laboriosus. By surface analysis, labor + -ious
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.