I

• I

iceberg

a regular winter swimmer
An individual who actually likes
swimming in spanner water.

an aussie institution since the 1930s

icy pole

a frozen lollypop

identity

an odd, interesting, or well-known person
Often reported as a well-known racing identity when referring to a suspected criminal.

since the 1870s

idiot box

television

iffy

of a suspicious nature

illywhacker

a small-time confidence trickster
Memorably revived by Peter Carey in his novel of the same name, published in 1985. It's origin is uncertain, possibly from pig Latin or backslang.

underworld slang of the 1940s

in a tick

very shortly

in fine feather

full of vitality and spirit

in it

anything done in the company of others
The it that you may be asked to be in may be physically or alcoholically exhausting.
Will you be in it?
Go on, be in it!
Goin' fishin' next Tuesday—be in it?

in like Flynn

assured of success in an enterprise
Originally meaning assured of a sexual conquest. Referring to aussie actor Errol Flynn, well‑known for his sexual adventures.
Interestingly, this term has been in use in the USA since the 1940s, but only in the non‑sexual sense.

originally wwii slang

in the chair

the person buying the drinks

in the know

having inside information

in the raw

naked

in the shit

in trouble
Also, in deep shit  meaning in serious trouble.

in the sticks

in remote rural areas

in the wars

going through a period of trouble, illness, or the like

in two shakes

in a short time

irrits

irritation, annoyance

iron lung ∼ wouldn't work in an iron lung

extraordinarily lazy