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 : at once, directly, forthwith, immediately, instantly, like a shot, now, straight off, straightaway
Meaning : At once (usually modifies an undesirable occurrence).
Example :
He promptly forgot the address.
Synonyms : promptly