The American Heritage® Dictionary of the English Language, 4th Edition
n. A hypothetical particle postulated to be the quantum of gravitational interaction and presumed to have an indefinitely long lifetime, zero electric charge, and zero rest mass. See Table at subatomic particle.
n. A hypothetical gauge boson that regulates the gravitational force. It would have a spin of 2 and zero rest mass.
the GNU version of the Collaborative International Dictionary of English
n. A theoretical gauge boson that mediates the (extremely weak) gravitational interactions between particles; the quantum of the gravitational field, having zero rest mass and a spin of 2.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a gauge boson that mediates the (extremely weak) gravitational interactions between particles
Word Usage
"Accordingly one attempts to treat the gravitational field as consisting of quantum - mechanical particles to which the name graviton has been given."