numb; insensitive (to physical sensation)
Describes a lack of physical sensation, such as numbness or insensitivity to pain, cold, or touch.
My fingers went numb from the cold.
He seems insensitive to pain.
apathetic; indifferent; callous
Describes emotional or moral insensitivity: indifference to others' feelings, lack of empathy, or being thick-skinned.
He is indifferent to the suffering of others.
His callous attitude hurt those around him.
無神経 focuses on tactlessness or lack of consideration for others, whereas 無感覚 can refer to a broader numbness or apathy.
Compound of 無 (mu, 'without') and 感覚 (kankaku, 'sensation, feeling'). The word follows standard Sino-Japanese word formation.