Meaning : Without delay or hesitation. With no time intervening.
Example :
He answered immediately.
Found an answer straightaway.
An official accused of dishonesty should be suspended forthwith.
Come here now!.
Synonyms : directly, forthwith, immediately, instantly, like a shot, now, right away, straight off, straightaway
Meaning : Simultaneously.
Example :
He took three cookies at a time.
Synonyms : at a time, at one time