One who has a thick skin; a person dull or slow of feeling. Also attributive.

(from A. II.)(a) A thing or person incapable of feeling; an inanimate thing; an apathetic person; (b) a person destitute of sense, a fool.

A person lacking natural feeling or moral sense. Obsolete.

A thing without feeling. Obsolete. rare.

One addicted to apathy, one sunk in stolid indifference.

A dull or awkward person, one who lacks geniality or liveliness. Also: a person who is unskilled or inept at something; (Theatre) an unconvincing…

With the and plural agreement: soulless people collectively.

figurative. colloquial. A dull, apathetic, unresponsive, or unthinkingly acquiescent person. Also as a general term of disparagement.