8 letters · 12 points in Scrabble
noun a gauge boson that mediates the (extremely weak) gravitational interactions between particles
originFrom gravity + -on. Coined by Russian physicists Dmitrii Blokhintsev and F. M. Gal'perin in 1934, and reintroduced by English physicist Paul Dirac in 1959 in a lecture to the American Physical Society.
Etymology from Wiktionary, CC BY-SA 3.0