Adverb

1. With the inside surface turned to be on the outside.

   I now realise that I have my shirt on inside out.

2. Of knowledge: Thoroughly, extremely well.

   I know IBM Assembler Language inside out.

   This is a contraction of the original phrase, 'inside and out', as in: She understands quantum mechanics inside and out.

1. Describes the hitting of a ball that pitched outside of leg stump to the off side of the field.

   He hit the ball inside out in an ugly manner, but scored a four.