1. 1. An inner or interior part.
   2. Inward character, perceptions, or feelings: felt good on the inside about volunteering to help.
2. An inner side or surface.
3. The part away from the edge; the middle part.
4. insides Informal.
   1. The inner organs; entrails.
   2. The inner parts or workings: the insides of a TV set.
5. Slang. Confidential or secret information.

1. Inner; interior.
2. Relating to, known to, or coming from an exclusive group: inside information; an inside joke.
3. Baseball. Passing on the side of home plate nearer the batter. Used of a pitch.

1. Into or in the interior; within.
2. On the inner side.
3. Slang. In prison.

1. Within: We'll be there inside an hour.
2. 1. On the inner side or part of: inside the package.
   2. Into the interior of: going inside the house.

inside out

1. With the inner surface turned out; reversed: wore the sweatshirt inside out.
2. InformalAs completely as possible; thoroughly:knew the city inside out. As completely as possible; thoroughly: knew the city inside out.

1. In a position of confidence or influence.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.