simple past tense and past participle of happen along

Accidents will happen, even when a project is carefully planned.

Synonym of it happens

(Internet, humorous) Unless one can provide the proof that one is requesting, that person has no credibility in the matter.

(colloquial) Bound to happen; absolutely to happen in the future.

(idiomatic) To realize, to bring about a thing.

(idiomatic) Sarcastically asserts that those in question thoroughly deserve their fate.

(idiomatic) A thing or situation which is almost certain to eventually lead to an accident

plural of accident waiting to happen

plural of disaster waiting to happen