Heartless means showing no pity at all. A heartless decision, utterly heartless, heartless of them.
It is a strong accusation and describes cruelty by indifference rather than by intention — a heartless rule is one nobody thought about. It is common in complaints about institutions: a heartless system. Note that the older meaning was lacking courage rather than lacking pity, which survives in nothing modern; and that heartless and heartfelt are opposites built on the same organ.
1adjectiveheartlessShowing no pity at all.
“It was a heartless decision and entirely within the rules.”
heartless is a quality of pitilessness.
Also accepted in games: merciless
Old English heortleas meant without courage — the heart was the seat of bravery before it was the seat of feeling. The modern sense is the same word after the metaphor moved.
Old English
heortlēas — without courage; listless
Middle English
hertles
English, today
heartless
From Middle English hertles, herteles, from Old English heortlēas (“without courage; listless”), equivalent to heart + -less. Cognate with German herzlos.
Etymology from Wiktionary, CC BY-SA