A statement, that
on its face is not threatening, but holds the
covert intent of possible damage.
example:
"You will get what's coming to you."
Spoken in monotone, without a smile, could be a veiled threat. If this same sentence were spoken with a smile in a lilting voice (with emphasis on the first 'you') it might be a promise of a reward.
Veiled threats are common weapons of organized crime bosses, high school principals and parents.