Question

What is Meant by a body at Rest? Or, What do You Mean by a body at Rest?

Answer 1

A body at rest may be defined as follows :

A body is said to be at rest, if it does not change its position with respect to a fixed point in its surroundings.

Or,

If the the position of a body remains unchanged with respect to any fixed point in its surroundings, then the body is said to be at rest.

For example -

A book laying on a table, if not disturbed by anybody, does not change its position with respect to the table, the walls of the room etc... So, a book laying on a table is at rest.