ruthless meaning , definition , what is ruthless : so determined to get what you want that ...: Learn more. The adjective ' ruthless ' has its etymological roots in the Old English word 'rūðlēas,' which can be broken down into 'rū,' meaning 'compassion' or 'pity,' and 'lēas,' meaning 'lacking' or 'without.' In its original form, 'rūðlēas' meant lacking compassion or pity, indicating a lack of mercy or remorse. Over time, this term transitioned into ' ruthless ' in modern English, retaining its fundamental meaning of being marked by a complete lack of compassion, empathy, or remorse, especially ... Ruthless means not caring about the pain or suffering of others, or determined to succeed without mercy. Learn more about the word, its synonyms, antonyms, and usage in sentences. ruthless definition : shows no mercy or compassion, often to achieve goals. Check meanings, examples, usage tips, pronunciation, domains, related words.