Synonyms and related words :
alert, apt, brief, compact, compendious, concise, curt, curtal, curtate, decisive, decurtate, expeditious, fast, hair-trigger, immediate, instant, lightning-like, little, low, momentaneous, momentary, presto, prompt, punctual, quick, quick as lightning, quick as thought, rapid, ready, short, short and sweet, speedy, spontaneous, succinct, summary, swift, synoptic, transient, transitory