A very brief time
A particular interval of time that is limited and often crucial
Occurring at once
Compelling immediate attention
on the instant
In an instant he was beside her, trying to take the bale from her hands.
In that instant the telephone rang.
In an instant they were in each other's arms.
She felt for his hand and knew an instant warm rush when she found it.
At last, however, the sea, as if weary of its new toy, threw me back on the shore, and in another instant I was clasped in my teacher's arms.