impetuous (adj.)
- abrupt
- accident-prone
- active
- acute
- adrift
- afloat
- aggressive
- alternating
- amorphous
- animated
- antsy
- anxious
- ardent
- breakneck
- breathless
- brisk
- brittle
- capricious
- careless
- changeable
- changeful
- corruptible
- deciduous
- desperate
- desultory
- devil-may-care
- dizzy
- dying
- dynamic
- eager
- eccentric
- edgy
- electrifying
- energetic
- enterprising
- enthusiastic
- ephemeral
- erratic
- evanescent
- excited
- fading
- fervid
- fickle
- fierce
- fiery
- fitful
- fleeting
- flickering
- flighty
- fluctuating
- fly-by-night
- flying
- forceful
- forcible
- fragile
- frail
- freakish
- fretful
- fugacious
- fugitive
- furious
- giddy
- harum-scarum
- hasty
- headlong
- hearty
- hopped-up
- hotheaded
- hurried
- impassioned
- impatient
- impermanent
- impulsive
- incisive
- inconsistent
- inconstant
- indecisive
- infirm
- insubstantial
- intense
- irregular
- irresolute
- irresponsible
- keen
- kinetic
- lively
- living
- lusty
- mad
- mazy
- mercurial
- mettlesome
- momentary
- moody
- mortal
- mutable
- offhand
- overeager
- overenthusiastic
- overhasty
- overzealous
- passing
- passionate
- peppy
- perishable
- precipitant
- precipitate
- precipitous
- quick
- rambling
- rash
- reckless
- restive
- restless
- robust
- roving
- rushing
- scatterbrained
- shapeless
- shifting
- shifty
- shocking
- short-lived
- slapdash
- snappy
- spanking
- spasmodic
- speedy
- spineless
- spirited
- spontaneous
- spur-of-the-moment
- startling
- stormy
- strenuous
- strong
- sudden
- surprising
- swift
- tempestuous
- temporal
- temporary
- transient
- transitive
- transitory
- trenchant
- unaccountable
- unanticipated
- uncertain
- uncontrolled
- undependable
- undisciplined
- uneasy
- unexpected
- unfixed
- unforeseen
- unlooked-for
- unplanned
- unpredictable
- unpredicted
- unpremeditated
- unquiet
- unreflective
- unreliable
- unrestrained
- unsettled
- unstable
- unsteady
- unthinking
- vacillating
- vagrant
- variable
- vehement
- vibrant
- vigorous
- violent
- vivacious
- vivid
- volatile
- volcanic
- wandering
- wanton
- wavering
- wavy
- wayward
- whimsical
- wild
- wishy-washy
- zestful
- zesty
- zippy
