Definition of heartless:
pachydermatous, inconsiderate, truculent, spiritless, take-no-prisoners, brutal, ironhearted, soulless, indurate, thoughtless, unkind, brute, fiendish, hard-hearted, insensible, vicious, cruel, inhuman, slash-and-burn, stonyhearted, uncharitable, attitude, desensitized, unthinking, flinty, pitiless, impersonal, obdurate, high-handed, insensate, affectless, butcherly, stony, unsparing, shameless, hardhearted, heavy-handed, sadistic, undiplomatic, inhumane, case-hardened, barbaric, remorseless, thick-skinned, unmerciful, savage, wanton, compassionless, barbarous, merciless, cold-hearted, atrocious.
insensitive (part of speech: adjective)
- "At Good Old Siwash", George Fitch.
- "The Vicar of Wrexhill", Mrs [Frances] Trollope.
- "Bad Hugh", Mary Jane Holmes.