Synonyms and Antonyms of at once
at one and the same time
- I have three papers due all at once.
- Call me at once when you get this message.
bang, directly, forthwith, headlong, immediately, incontinently, instantaneously, instanter, instantly, now, PDQ, plumb, presently, promptly, pronto, right, right away, right now, right off, straightaway, straight off, straightway
anon, momentarily, shortly, soon
apace, briskly, fast, fleetly, full-tilt, posthaste, quick, quickly, rapidly, readily, snappily, speedily, swift, swiftly
abruptly, presto, suddenly, unexpectedly
hastily, impetuously, impulsively, rashly, recklessly
exactly, opportunely, punctually, seasonably