arduous backbreaking back-breaking grueling gruelling hard heavy laborious labourious punishing slavish strenuous toilsome

effortful effortful adj. 1. requiring great physical effort. Opposite of {effortless}. [Narrower terms: {arduous, backbreaking, back-breaking, grueling, gruelling, hard, heavy, laborious, labourious, punishing, slavish, strenuous, toilsome}; {exhausting, tiring, wearing, wearying}] Also See: {difficult}, {hard}. [WordNet 1.5]