boson

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of a class of particles, including photons, mesons, or alpha particles, that have integral spins and do not obey the exclusion principle, so that any number of identical particles may occupy the same quantum state.

from The Century Dictionary.

• noun A bolt for the crossbow, having a round knob at the end, with a small point projecting from it.
• noun A corruption of boatswain, representing its common pronunciation.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) A fundamental particle that obeys Bose-Einstein statistical rules, but not the Pauli exclusion principle; the spin value of a boson is always an integer. Examples of bosons are alpha particles, photons, and those nuclei which have an even mass number.
• noun obsolete See boatswain.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics A particle with totally symmetric composite quantum states, which exempts them from the Pauli exclusion principle, and that obey Bose-Einstein statistics. They have integer spin. Among them are many elementary particles, and some (gauge bosons) are known to carry the fundamental forces. Compare fermion.
• noun obsolete A boatswain.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle; all nuclei with an even mass number are bosons