A single verb for "unwittingly letting something happen"?

Question

Is there a single-word verb that means "to miss something dangerous and let something adverse happen unwittingly", with the emphasis on unwittingly?

In Russian, this exact meaning is conveyed by a series of (perfective) verbs: "provoronit'" (проворонить), "prozevat'" (прозевать), "proglyadet'" (проглядеть). All three take a direct object, usually denoting the exact cause of the adverse situation in question (less frequently, the situation itself).

All three, in most usage cases, convey the following meanings simultaneously:

1. the direct object of the verb, the missed fact, spawned a situation that entails damage or adverse conditions, it's not mere discomfort or missed opportunity for improvement;
2. the subject actually failed to notice anything wrong (because of being either inattentive or overworked): 2.1. the subject did not turn a blind eye to the situation, 2.2. neither did they contemplate taking steps to prevent it but decided against action;
3. the damage was a genuine screw-up — all three verbs rule out any malafide inaction or other plans for benefitting from the adverse situation;
4. there were reasonable, often easy, steps to prevent the situation altogether; but none were taken due to p.2.

To top it off, while "prozevat'" has an accusative connotation of undue inattentiveness, "proglyadet'" often bears an exonerative connotation since its primary, literal meaning is to "skim (a text)", usually because of an unreasonable amount of paperwork.

To my feelings, the broadly corresponding verbs "miss something", "pass up something", "overlook something", "waste something" and "blow something" don't fit exactly in the above semantics:

• "to miss" often pairs with "opportunity" and other positively-marked objects, and the fact of missing often implies but doesn't guarantee damage or suffering in all use cases (not p.1);
• "pass up" may mean "thinking about but deciding against, to one's own dislike" (not p.2.1);
• "overlook" doesn't always rule out turning a blind eye, may mean "consciously ignore" (not p.2.2);
• "waste" and "blow" don't rule out a slacking attitude or a shoddy execution, i.e. steps actually were taken, but were insufficient (not p.4 and thereby not p.2).

Is there a one-word for "things were unwittingly missed, things went sideways, nobody ever planned to profit from that"? If possible, is there a pair with an accusative connotation and an exonerative one?

Answer 1

"to miss something dangerous and let something adverse happen unwittingly"

to summarise "To unintentionally make a dangerous mistake"

The nearest I can think of is

cock-up; noun [ C ] UK slang; something that is done wrong or badly: Ref C.E.D

It is not the same and actually covers a bigger range of mistakes and how they are made. The definition not being so restrictive as your post. However it does include the majority of the points listed so eloquently above. It can equally relate to trivial, minor, dangerous or huge mistakes.