WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
an elementary particle responsible for the forces in the atomic nucleus; a hadron with a baryon number of 0
Word Usage
"We can't fit anything really powerful into a Hevian rocket plane-a pile would go into one easily enough, but a frictionator or a naval - size mesotron rifle wouldn't, and there'd be no point in taking popguns."