icing sugar: n powdered/confectioner’s sugar. The very fine sugar used to make cake icing.
ickle: n itty-bitty; very small. Usually be seen in use regarding “cute” things: What an ickle puppy! Less likely to be seen in more serious situations: Dad - I’ve just had an ickle accident in your car.
indeed: adv extra-much, when used after a statement: It was pretty warm to start with but when they turned on the booster rockets it got very hot indeed.
indicator: n turn signal. The little orange lights that flash on the side of the car to show that you’re about to frantically try and turn across four lanes of traffic into your driveway.
innit: interj London “isn’t it.” A very London-centric contraction with nasal pronunciation obligatory: Well, the traffic’s always this bad at this time of night, innit guvnor.
interval: n intermission. The break in a stage performance where the audience can go off to have a pee and get some more beers in. At a stretch it could refer to the period of time in which advertisements are shown on television, though Brits more commonly refer to that as the “break.”
ironmonger: n hardware shop. A bit of an antiquated word.