IPA: /ˈhɑːrtləs/
KK: /ˈhɑrtləs/
Lacking kindness or compassion; showing no sympathy for others.
His heartless actions left many people feeling hurt and abandoned.
Heartless → It is formed from "heart" (from Old English "heorte", meaning the organ that pumps blood and also symbolizes emotion) and "-less" (meaning without). The word "heartless" describes a state of being without heart, or lacking compassion and emotion.
Think of someone who is 'without' ('-less') 'heart' — this helps you remember that 'heartless' means lacking compassion or emotion.