The Collaborative International Dictionary of English v.0.48:

H \H\ ([=a]ch),
   the eighth letter of the English alphabet, is classed among
   the consonants, and is formed with the mouth organs in the
   same position as that of the succeeding vowel. It is used
   with certain consonants to form digraphs representing sounds
   which are not found in the alphabet, as sh, th, [th], as in
   shall, thing, [th]ine (for zh see [sect]274); also, to modify
   the sounds of some other letters, as when placed after c and
   p, with the former of which it represents a compound sound
   like that of tsh, as in charm (written also tch as in catch),
   with the latter, the sound of f, as in phase, phantom. In
   some words, mostly derived or introduced from foreign
   languages, h following c and g indicates that those
   consonants have the hard sound before e, i, and y, as in
   chemistry, chiromancy, chyle, Ghent, Ghibelline, etc.; in
   some others, ch has the sound of sh, as in chicane. See Guide
   to Pronunciation, [sect][sect] 153, 179, 181-3, 237-8.
   [1913 Webster]

   Note: The name (aitch) is from the French ache; its form is
         from the Latin, and this from the Greek H, which was
         used as the sign of the spiritus asper (rough
         breathing) before it came to represent the long vowel,
         Gr. [eta]. The Greek H is from Ph[oe]nician, the
         ultimate origin probably being Egyptian. Etymologically
         H is most closely related to c; as in E. horn, L.
         cornu, Gr. ke`ras; E. hele, v. t., conceal; E. hide, L.
         cutis, Gr. ky`tos; E. hundred, L. centum, Gr.
         "e-kat-on, Skr. [.c]ata.
         [1913 Webster]

   H piece (Mining), the part of a plunger pump which contains
      the valve.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

H \H\ (h[aum]). (Mus.)
   The seventh degree in the diatonic scale, being used by the
   Germans for B natural. See B.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ion \I"on\ ([imac]"[o^]n), n. [Gr. 'io`n, neut, of 'iw`n, p. pr.
   of 'ie`nai to go.]
   1. (Elec. Chem.) an atom or goup of atoms (radical) carrying
      an electrical charge. It is contrasted with neutral atoms
      or molecules, and free radicals. Certain compounds, such
      as sodium chloride, are composed of complementary ions in
      the solid (crystalline) as well as in solution. Others,
      notably acids such as hydrogen chloride, may occur as
      neutral molecules in the pure liquid or gas forms, and
      ionize almost completely in dilute aqueous solutions. In
      solutions (as in water) ions are frequently bound
      non-covalently with the molecules of solvent, and in that
      case are said to be solvated. According to the
      electrolytic dissociation theory, the molecules of
      electrolytes are divided into ions by water and other
      solvents. An ion consists of one or more atoms and carries
      one unit charges of electricity, 3.4 x 10^-10
      electrostatic units, or a multiple of this. Those which
      are positively electrified (hydrogen and the metals) are
      called cations; negative ions (hydroxyl and acidic atoms
      or groups) are called anions.

   Note: Thus, hydrochloric acid (HCl) dissociates, in aqueous
         solution, into the hydrogen ion, H+, and the chlorine
         ion, Cl-; ferric nitrate, Fe(NO3)3, yields the
         ferric ion, Fe+++, and nitrate ions, NO3-, NO3-,
         NO3-. When a solution containing ions is made part of
         an electric circuit, the cations move toward the
         cathode, the anions toward the anode. This movement is
         called migration, and the velocity of it differs for
         different kinds of ions. If the electromotive force is
         sufficient, electrolysis ensues: cations give up their
         charge at the cathode and separate in metallic form or
         decompose water, forming hydrogen and alkali;
         similarly, at the anode the element of the anion
         separates, or the metal of the anode is dissolved, or
         decomposition occurs. Aluminum and chlorine are
         elements prepared predominantly by such electrolysis,
         and depends on dissolving compounds in a solvent where
         the element forms ions. Electrolysis is also used in
         refining other metals, such as copper and silver. Cf.
         Anion, Cation.
         [Webster 1913 Suppl.]

   2. One of the small electrified particles into which the
      molecules of a gas are broken up under the action of the
      electric current, of ultraviolet and certain other rays,
      and of high temperatures. To the properties and behavior
      of ions the phenomena of the electric discharge through
      rarefied gases and many other important effects are
      ascribed. At low pressures the negative ions appear to be
      electrons; the positive ions, atoms minus an electron. At
      ordinary pressures each ion seems to include also a number
      of attached molecules. Ions may be formed in a gas in
      various ways.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

H
    n 1: a nonmetallic univalent element that is normally a
         colorless and odorless highly flammable diatomic gas; the
         simplest and lightest and most abundant element in the
         universe [syn: hydrogen, H, atomic number 1]
    2: a unit of inductance in which an induced electromotive force
       of one volt is produced when the current is varied at the
       rate of one ampere per second [syn: henry, H]
    3: the constant of proportionality relating the energy of a
       photon to its frequency; approximately 6.626 x 10^-34 joule-
       second [syn: Planck's constant, h]
    4: the 8th letter of the Roman alphabet [syn: H, h]
    5: (thermodynamics) a thermodynamic quantity equal to the
       internal energy of a system plus the product of its volume
       and pressure; "enthalpy is the amount of energy in a system
       capable of doing mechanical work" [syn: heat content,
       total heat, enthalpy, H]

The Jargon File (version 4.4.7, 29 Dec 2003):

h


    [from SF fandom] A method of ?marking? common words, i.e., calling
    attention to the fact that they are being used in a nonstandard, ironic, or
    humorous way. Originated in the fannish catchphrase ?Bheer is the One True
    Ghod!? from decades ago. H-infix marking of ?Ghod? and other words spread
    into the 1960s counterculture via underground comix, and into early
    hackerdom either from the counterculture or from SF fandom (the three
    overlapped heavily at the time). More recently, the h infix has become an
    expected feature of benchmark names (Dhrystone, Rhealstone, etc.); this is
    probably patterning on the original Whetstone (the name of a laboratory)
    but influenced by the fannish/counterculture h infix.


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

h

   1. A simple markup language intended for quick conversion of
   existing text to hypertext.

   2. A method of marking common words to call attention to the
   fact that they are being used in a nonstandard, ironic, or
   humorous way.  Originated in the fannish catchphrase "Bheer
   is the One True Ghod!" from decades ago.  H-infix marking of
   "Ghod" and other words spread into the 1960s counterculture
   via underground comix, and into early hackerdom either from
   the counterculture or from SF fandom (the three overlapped
   heavily at the time).  More recently, the h infix has become
   an expected feature of benchmark names (Dhrystone, Rhealstone,
   etc.); this follows on from the original Whetstone (the name
   of a laboratory) but may have been influenced by the
   fannish/counterculture h infix.

   [Jargon File]

   (1994-11-04)