The Collaborative International Dictionary of English v.0.48:

Vital \Vi"tal\, a. [F., fr. L. vitalis, fr. vita life; akin to
   vivere to live. See Vivid.]
   1. Belonging or relating to life, either animal or vegetable;
      as, vital energies; vital functions; vital actions.
      [1913 Webster]

   2. Contributing to life; necessary to, or supporting, life;
      as, vital blood.
      [1913 Webster]

            Do the heavens afford him vital food? --Spenser.
      [1913 Webster]

            And vital virtue infused, and vital warmth.
                                                  --Milton.
      [1913 Webster]

   3. Containing life; living. "Spirits that live throughout,
      vital in every part." --Milton.
      [1913 Webster]

   4. Being the seat of life; being that on which life depends;
      mortal.
      [1913 Webster]

            The dart flew on, and pierced a vital part. --Pope.
      [1913 Webster]

   5. Very necessary; highly important; essential.
      [1913 Webster]

            A competence is vital to content.     --Young.
      [1913 Webster]

   6. Capable of living; in a state to live; viable. [R.]
      [1913 Webster]

            Pythagoras and Hippocrates . . . affirm the birth of
            the seventh month to be vital.        --Sir T.
                                                  Browne.
      [1913 Webster]

   Vital air, oxygen gas; -- so called because essential to
      animal life. [Obs.]

   Vital capacity (Physiol.), the breathing capacity of the
      lungs; -- expressed by the number of cubic inches of air
      which can be forcibly exhaled after a full inspiration.

   Vital force. (Biol.) See under Force. The vital forces,
      according to Cope, are nerve force (neurism), growth force
      (bathmism), and thought force (phrenism), all under the
      direction and control of the vital principle. Apart from
      the phenomena of consciousness, vital actions no longer
      need to be considered as of a mysterious and unfathomable
      character, nor vital force as anything other than a form
      of physical energy derived from, and convertible into,
      other well-known forces of nature.

   Vital functions (Physiol.), those functions or actions of
      the body on which life is directly dependent, as the
      circulation of the blood, digestion, etc.

   Vital principle, an immaterial force, to which the
      functions peculiar to living beings are ascribed.

   Vital statistics, statistics respecting the duration of
      life, and the circumstances affecting its duration.

   Vital tripod. (Physiol.) See under Tripod.

   Vital vessels (Bot.), a name for latex tubes, now disused.
      See Latex.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Vital \Vi"tal\, n.
   A vital part; one of the vitals. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

vital
    adj 1: urgently needed; absolutely necessary; "a critical
           element of the plan"; "critical medical supplies"; "vital
           for a healthy society"; "of vital interest" [syn:
           critical, vital]
    2: performing an essential function in the living body; "vital
       organs"; "blood and other vital fluids"; "the loss of vital
       heat in shock"; "a vital spot"; "life-giving love and praise"
       [syn: vital, life-sustaining]
    3: full of spirit; "a dynamic full of life woman"; "a vital and
       charismatic leader"; "this whole lively world" [syn: full of
       life, lively, vital]
    4: manifesting or characteristic of life; "a vital, living
       organism"; "vital signs"

Moby Thesaurus II by Grady Ward, 1.0:

224 Moby Thesaurus words for "vital":
   abiding, aboveground, acid, age-long, aged, agog, alacritous,
   alive, alive and kicking, all agog, among the living, ancient,
   animate, animated, animating, antic, antique, anxious, armipotent,
   authoritative, avid, bang, basic, bedrock, biological, biotic,
   biting, bouncing, breathing, breathless, brisk, bursting to,
   called for, capable of life, capersome, cardinal, central, chronic,
   cogent, coltish, compulsory, conscious, constant, constitutive,
   continuing, corrosive, critical, crucial, cutting, desirous,
   diuturnal, drive, driving, durable, dynamic, eager, effective,
   endowed with life, enduring, energetic, enlivened, enlivening,
   essential, evergreen, existent, exuberant, flush, focal, forceful,
   forcible, forward, frisky, frolicsome, full of beans, full of life,
   fundamental, gamesome, gay, getup, gutsy, hale, hale and hearty,
   hardy, hearty, high-potency, high-powered, high-pressure,
   high-tension, immutable, impatient, imperative, important,
   impressive, in force, in power, in the flesh, incisive, indicated,
   indispensable, inspirited, instinct with life, integral,
   intransient, inveterate, invigorating, irreducible, irreductible,
   irreplaceable, irresistible, keen, key, lasting, life-and-death,
   life-giving, life-or-death, live, lively, living, long-lasting,
   long-lived, long-standing, long-term, longeval, longevous, lusty,
   macrobiotic, main, mandatory, material, mighty, mighty in battle,
   mordant, necessary, needed, needful, nervous, of long duration,
   of long standing, of vital importance, operative, organic,
   organized, panting, paramount, penetrating, perdurable, perduring,
   perennial, permanent, perpetual, persistent, persisting,
   physiological, piercing, pivotal, playful, poignant, potent,
   powerful, prepotent, prerequisite, prompt, puissant, punchy, quick,
   quickening, raring to, ready, ready and willing, red-blooded,
   rejuvenating, remaining, required, requisite, reviving, robust,
   robustious, robustuous, rollicking, rollicksome, rompish, rude,
   rugged, ruling, sempervirent, sensational, sinewed, sinewy,
   skittish, slashing, spirited, sportive, sprightly, stable,
   stalwart, staying, steadfast, stout, strenuous, striking, strong,
   sturdy, substantive, telling, tenacious of life, tough, trenchant,
   unfading, unforgoable, valid, very much alive, viable, vigorous,
   vim, vitality, vitalizing, vivacious, vivid, vivified, vivifying,
   wanted, zestful, zippy, zoetic



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

VITAL
       VHDL Initiative Toward ASIC Libraries (ASIC, VHDL)


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

VITAL

   A semantics language using FSL, developed by Mondshein in
   1967.

   [Sammet 1969, p. 641].

   (1995-02-23)