It means Harmful in an unexpected way. Can't help you with a sentence I am trying get one for it myself Okay, heres an example, hope it helps! >.< The deleterious effects of smoking include...
Smoking is known to be deleterious to your health.
Police charged the attacker with assault with intent to prevent arrest and possession of a deleterious substance.
Divorce can have deleterious effects on children.
Notwithstanding its deleterious long-term effects, I enjoy a cigarette almost every morning, as it redounds positively to my mood.