- 1 [countable, usually singular] (also the inside) the inner part, side or surface of something The inside of the box was blue. The door was locked from the inside. The shell is smooth on the inside. the insides of the windows opposite outside
- 2the inside [singular] the part of a road nearest the edge, that is used by slower vehicles He tried to overtake on the inside. opposite outside See related entries: Features of roads
- 3the inside [singular] the part of a curved road or track nearest to the middle or shortest side of the curve The French runner is coming up fast on the inside. opposite outside
- 4insides [plural] (informal) a person’s stomach and bowels She was so nervous, her insides were like jelly. He complained of a pain in his insides. Word Origin late Middle English (denoting the interior of the body): from in + side.Idioms with the part that is usually inside facing out You've got your sweater on inside out. Turn the bag inside out and let it dry. compare back to front
- 1to make a place very untidy when you are searching for something The burglars had turned the house inside out.
- 2to cause large changes The new manager turned the old systems inside out.
(informal) to be very familiar with somebody/something This is where I grew up. I know this area like the back of my hand. belonging to a group or an organization and therefore able to get information that is not available to other people The thieves must have had someone on the inside helping them.