Source : Webster's Revised Unabridged Dictionary (1913)

Boil \Boil\ (boil), v. i. [imp. & p. p. {Boiled} (boild); p. pr.
   & vb. n. {Boiling}.] [OE. boilen, OF. boilir, builir, F.
   bouillir, fr. L. bullire to be in a bubbling motion, from
   bulla bubble; akin to Gr. ?, Lith. bumbuls. Cf. {Bull} an
   edict, {Budge}, v., and {Ebullition}.]
   1. To be agitated, or tumultuously moved, as a liquid by the
      generation and rising of bubbles of steam (or vapor), or
      of currents produced by heating it to the boiling point;
      to be in a state of ebullition; as, the water boils.

   2. To be agitated like boiling water, by any other cause than
      heat; to bubble; to effervesce; as, the boiling waves.

            He maketh the deep to boil like a pot. --Job xii.
                                                  31.

   3. To pass from a liquid to an a["e]riform state or vapor
      when heated; as, the water boils away.

   4. To be moved or excited with passion; to be hot or fervid;
      as, his blood boils with anger.

            Then boiled my breast with flame and burning wrath.
                                                  --Surrey.

   5. To be in boiling water, as in cooking; as, the potatoes
      are boiling.

   {To boil away}, to vaporize; to evaporate or be evaporated by
      the action of heat.

   {To boil over}, to run over the top of a vessel, as liquid
      when thrown into violent agitation by heat or other cause
      of effervescence; to be excited with ardor or passion so
      as to lose self-control.

Boiling \Boil"ing\, n.
   1. The act of ebullition or of tumultuous agitation.

   2. Exposure to the action of a hot liquid.

Boiling \Boil"ing\, a.
   Heated to the point of bubbling; heaving with bubbles; in
   tumultuous agitation, as boiling liquid; surging; seething;
   swelling with heat, ardor, or passion.

   {Boiling point}, the temperature at which a fluid is
      converted into vapor, with the phenomena of ebullition.
      This is different for different liquids, and for the same
      liquid under different pressures. For water, at the level
      of the sea, barometer 30 in., it is 212 [deg] Fahrenheit;
      for alcohol, 172.96[deg]; for ether, 94.8[deg]; for
      mercury, about 675[deg]. The boiling point of water is
      lowered one degree Fahrenheit for about 550 feet of ascent
      above the level of the sea.

   {Boiling spring}, a spring which gives out very hot water, or
      water and steam, often ejecting it with much force; a
      geyser.

   {To be at the boiling point}, to be very angry.

   {To keep the pot boiling}, to keep going on actively, as in
      certain games. [Colloq.]

Source : WordNet®

boiling
     n 1: the application of heat to change something from a liquid to
          a gas
     2: cooking in a boiling liquid [syn: {stewing}, {simmering}]

boiling
     adv : extremely; "boiling mad"