36 synonyms for immediately such as as soon as possible, asap, and as fast as possible. Immediately is an adverb, and its antonyms are eventually and delayed.
ASAP, as fast as possible, as soon as possible, at once, directly, double quick, ekdam, fast, forthright, forthwith, here and now, in a flash, in double quick time, instanter, instantly, now, p.d.q. (pretty damn quick), post-haste, promptly, pronto, quickly, right away, right now, speedily, straight away, straightway, there and then, this/that (very) minute, this/that instant, toot sweet, tout de suite, with all speed, without delay, without further ado, and without hesitation.