- illy-whacker
- in days of yore
- in a bad way
- incumbency
- in short order
- incorruptibility
- in the sticks
- ince-ssantly
- in the nuddy
- in many cases
- idolized
- instantane-ous
- incomings
- imprimatur
- inconstantly
- in a good mood
- in the matter of
- informal pretty much
- in the scud
- in rude health
- in big
- in good shape
- in ancient Rome circus
- in many instances
- interdicted
- in the back-blocks
- in a dither
- ire-versible
- itemized
- itsy-bitsy
- in plenty
- in time of yore
- innovators
- irregligious
- irreconci-lable
- in double quick time
- impressiveness
- intransigence
- itty-bitty
- invalided
- in Queer Street
- in the ballpark of
- in flap
- iniquitous nefarious
- ill-conceived
- in good trim
- in abundance
- itch for
- in the tall timbers
- incurvation
- in transports of delight
- in a state
- in fine fettle
- in jig time
- in a blue funk
- in a tiz-woz
- in a huff
- incomprehensible
- indefatigability
- in a cold sweat
- in trim
- in a tiz
- in a lather
- informal you got it
- in the boondocks
- insightful
- intrinsically
- ill-thought-out
- in low spirits
- inherently
- in one's best interests
- in a split scond
- in a tizz
- informl chuck up
- in a tizzy
- in-effectual
- ickle
- in double-quick time
- interstate
- illywhacker
- in the twinkling of an eye
- instanter
- in every way
- in no time at all
- in left field
- in every respect
- in a paddy
- in a stew
- in a twitter
- is that a fact
- in the bag
- I never did
- I'll be blowed
- in a twit