The Collaborative International Dictionary of English v.0.48:

lepton \lepton\ n. (Physics)
   an elementary particle that participates in weak interactions
   but does not participate in the strong interaction; it has a
   baryon number of 0. Some known leptons are the electron,
   the negative muon, the tau-minus particle, and the
   neutrinos associated with each of these particles.
   [WordNet 1.5 +PJC]

The Collaborative International Dictionary of English v.0.48:

Electron \E*lec"tron\, n. [NL., fr. Gr. 'h`lektron. See
   Electric.]
   1. Amber; also, the alloy of gold and silver, called
      electrum. [archaic]
      [1913 Webster]

   2. (Physics & Chem.) one of the fundamental subatomic
      particles, having a negative charge and about one
      thousandth the mass of a hydrogen atom. The electron
      carries (or is) a natural unit of negative electricity,
      equal to 3.4 x 10^-10 electrostatic units, and is
      classed by physicists as a lepton. Its mass is
      practically constant at the lesser speeds, but increases
      due to relativistic effects as the velocity approaches
      that of light. Electrons are all of one kind, so far as is
      known. Thus far, no structure has been detected within an
      electron, and it is probably one of the ultimate composite
      constituents of all matter. An atom or group of atoms from
      which an electron has been detached has a positive charge
      and is called a cation. Electrons are projected from the
      cathode of vacuum tubes (including television picture
      tubes) as cathode rays and from radioactive substances
      as the beta rays. Previously also referred to as
      corpuscle, an obsolete term. The motion of electrons
      through metallic conductors is observed as an electric
      current. A particle identical to the electron in mass and
      most other respects, but having a positive instead of a
      negative charge, is called a positron, or antielectron
      [Webster 1913 Suppl. +PJC] Electro-negative

WordNet (r) 3.0 (2006):

electron
    n 1: an elementary particle with negative charge [syn:
         electron, negatron]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "electron":
   Kern, NMR, alpha particle, antibaryon, antilepton, antimeson, atom,
   atomic nucleus, atomic particle, baryon, beta particle,
   cathode particle, electron affinity, electron cloud, electron pair,
   electron shells, electron spin, electron transfer,
   electron-positron pair, elementary particle, energy level,
   excited state, extranuclear electrons, ground state, ion, lepton,
   lone pair, meson, molecule, monad, negatron, neutron,
   nuclear force, nuclear magnetic resonance, nuclear particle,
   nuclear resonance, nucleon, nucleosynthesis, nucleus, octet,
   orbital electron, photoelectron, photon, proton, quark,
   recoil electron, secondary electron, shared pair, strangeness,
   strong interaction, subvalent electrons, surface-bound electron,
   thermion, triton, valence electron, valence electrons,
   valence shell, wandering electron



The Free On-line Dictionary of Computing (30 December 2018):

electron

    A sub-atomic particle with a negative quantised
   charge.  A flow of electrical current consists of the
   unidirectional (on average) movement of many electrons.  The
   more mobile electrons are in a given material, the greater it
   electrical conductance (or equivalently, the lower its
   resistance).

   (1995-10-06)