just before; on the verge of; at the point of
Used as a suffix-like noun attached to verbs or nouns indicating an event, meaning the moment immediately before that event. Common with 出発, 帰宅, 死, etc.
I noticed I had forgotten something just before departure.
彼は死の間際に家族の名前を呼んだ。
He called his family's names on the verge of death.
Rare standalone use; typically appears in the same suffix-like construction as sense 1, emphasizing the physical or temporal edge just before an event. Often interchangeable with sense 1.
崖の間際に立つと足がすくむ。
My legs freeze when I stand at the very edge of the cliff.
Just before departure, I noticed I'd forgotten something.
I suddenly got nervous right before the exam.
I wish they wouldn't change the plan at the last moment.