- Impulsiveness
- Impure
- Impurity
- In a fair way
- In a flat spin
- In a low-tune
- In a matter of seconds
- In a sorry pickle
- In a stew
- In absentia
- In at the kill
- In bad faith
- In deep mourning
- In dignify
- In extremis
- In fawn
- In fear and trembling
- In flood of tears
- In foal
- In general
- In glowing terms
- In jest
- In less than no time
- In letter and spirit
- In memoriam
- In mint condition
- In name
- In no case
- In one's fifties
- In ones own name
- In ones own time
- In ones tracks
- In ordination
- In parts
- In place of
- In public
- In queer street
- In rags
- In relation to
- In respect that
- In sackcloth and ashes
- In separate lots
- In some sort
- In spirits
- In spite of oneself
- Incurious
- In tatters
- In the dust
- In the family way
- In the land of the living
- In the least
- In the long run
- In the making
- In the public domain
- In the public eye
- In the round
- In the saddle
- In time
- In toto
- In two minds
- In vain
- In-service
- Ina high pitch
- Inaccuracy
- Inactivity
- Inadvertent
- Inalienably
- Inaniloquent
- Inapt
- Inattention
- Inaugurates
- Inauspicious woman
- Inboard
- Inborn
- Inbred
- Incantation
- Incapacity
- Incarcerate
- Incarcerated
- Incendiarism
- Incendiary
- Inchoate
- Inchoation
- Incident
- Incidentally
- Incinerator
- Incise
- Incite
- Incite children
- Incitement
- Inclination
- Inclosure
- Including
- incoagulable
- Incognita
- Incognito
- Incoming
- Incommensurably
- Incomparably
- Incompatible