suddenly

instantaneously

Occurring without time passing

• precipitouslyExtremely steeply or hastily
• instantlyWithout any pause
• quicklyAt high speed

rapidly · swiftly · all at once · in a flash · in an instant · without warning · out of nowhere · sharply · curtly · brusquely

unexpectedly

Without prior indication

• unforeseenNot predicted or expected
• unanticipatedNot predicted beforehand
• out of the blueWithout any forewarning

startlingly · shockingly · astonishingly · surprisingly · unpredictably · catch off guard · blindsided · bolt from the blue · unlooked-for · unaware

jolt

Abrupt forceful shake

• startleFrighten suddenly
• stunDaze by force
• astoundShock with wonder

alarm · thunderstruck · bombshell · jarring · rattled · shaken · reeling · gut punch · whiplash · double take

lo and behold

Exclamation announcing surprise

• voilàExclamation presenting something
• prestoVery fast tempo
• bangSudden loud noise

boom · wham · bam · whoosh · flash · poof · snap · crack · like magic · in a heartbeat

halt

Complete sudden stop

• stopCease all motion
• breakInterrupt continuity
• snapSudden sharp sound

cut short · disruption · cease · suspension · derail · terminate · discontinue · truncate · sever · arrest

• -LY wordssoftly, loudly, quickly, slowly, happily
• adverbsquickly, slowly, very, really, now
• instantlyinstantly, immediately, at once, in a flash, in an instant
• sudden thingsunexpectedly, instantly, spontaneous, surprise, shock
• suddennessabrupt, instant, instantly, immediate, immediately
• timesecond, minute, hour, day, seconds