Example : If I had the chance I'd do it in a flash.

Synonyms : blink of an eye, flash, heartbeat, jiffy, new york minute, split second, trice, twinkling, wink

Example : The moment he arrived the party began.

Synonyms : minute, moment, second

Example : Relief was instantaneous.
Instant gratification.

Synonyms : instantaneous

Example : Your letter of the 10th inst.

Synonyms : inst

Example : Clamant needs.
A crying need.
Regarded literary questions as exigent and momentous.
Insistent hunger.
An instant need.

Synonyms : clamant, crying, exigent, insistent