ˈn(y)ü.ˌträn noun
( -s )
Etymology: probably from neutr al (I) + -on
: an uncharged elementary particle that has a mass nearly equal to that of the proton, that by itself is unstable with an average lifetime of 1013 seconds, that can be stabilized when joined to a proton, and that is present in all known atomic nuclei except the lightest hydrogen nucleus