deleterious

adj

Etymology: Adapted borrowing (1640s; 1582 as deletorious) of New Latin dēlētērius, dēlētōrius + -ous, from Ancient Greek δηλητήριος (dēlētḗrios, “noxious, deleterious”), from δηλητήρ (dēlētḗr, “a destroyer”), from δηλέομαι (dēléomai, “I hurt, damage, spoil, waste”). Not related to delete or deleble. Doublet of deletery.

1. Harmful, often in a subtle or unexpected way.

   “deleterious effects”

   “deleterious to someone's health”

2. Having lower fitness.

   “A deleterious mutation”