What does "rest energy" mean?

The energy of the mass component of a body at rest; equal to the product of its rest mass and the square of the speed of light

What is a synonym for "rest energy"?

Common synonyms include: mass dependent energy, mass energy.

noun

noun ·Rare ·Advanced level

Noun

1
The energy of the mass component of a body at rest; equal to the product of its rest mass and the square of the speed of light
2
the energy equivalent to the mass of a particle at rest in an inertial frame of reference; equal to the rest mass times the square of the speed of light wordnet