The Collaborative International Dictionary of English v.0.48:

Gist \Gist\ (j[i^]st), n. [OF. giste abode, lodgings, F.
   g[^i]te, fr. g['e]sir to lie, L. jac[=e]re, prop., to be
   thrown, hence, to lie, fr. jac[e^]re to throw. In the second
   sense fr. OF. gist, F. g[^i]t, 3d pers. sing. ind. of
   g['e]sir to lie, used in a proverb, F., c'est l[`a] que
   g[^i]t le li[`e]vre, it is there that the hare lies, i. e.,
   that is the point, the difficulty. See Jet a shooting
   forth, and cf. Agist, Joist, n., Gest a stage in
   traveling.]
   1. A resting place. [Obs.]
      [1913 Webster]

            These quails have their set gists; to wit, ordinary
            resting and baiting places.           --Holland.
      [1913 Webster]

   2. The main point, as of a question; the point on which an
      action rests; the pith of a matter; as, the gist of a
      question.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gist
    n 1: the central meaning or theme of a speech or literary work
         [syn: effect, essence, burden, core, gist]
    2: the choicest or most essential or most vital part of some
       idea or experience; "the gist of the prosecutor's argument";
       "the heart and soul of the Republican Party"; "the nub of the
       story" [syn: kernel, substance, core, center,
       centre, essence, gist, heart, heart and soul,
       inwardness, marrow, meat, nub, pith, sum, nitty-
       gritty]

Moby Thesaurus II by Grady Ward, 1.0:

160 Moby Thesaurus words for "gist":
   affective meaning, axiom, basis, bearing, bench mark, best part,
   better part, body, bulk, burden, cardinal point, case, center,
   chapter, chief thing, climax, coloring, concern, connotation,
   consequence, core, cornerstone, crisis, critical point, crux,
   denotation, direction, distillate, distillation, drift, effect,
   elixir, essence, essential, essential matter, extension, fabric,
   flower, focus, focus of attention, focus of interest, force,
   fundamental, generality, grammatical meaning, gravamen,
   great point, head, heading, heart, high point, hypostasis, idea,
   impact, implication, import, important thing, inner essence,
   intension, issue, kernel, keystone, landmark, lexical meaning,
   literal meaning, living issue, main body, main idea, main point,
   main thing, major part, majority, marrow, mass, material,
   material point, matter, matter in hand, meaning, meat, medium,
   milestone, most, motif, motive, nub, nucleus, nuts and bolts,
   overtone, pertinence, pith, pivot, plurality, point,
   point at issue, point in question, postulate,
   practical consequence, principle, problem, purport, question, quid,
   quiddity, quintessence, range of meaning, real issue, real meaning,
   recap, recapitulation, reference, referent, relation, relevance,
   resume, rubric, run-through, rundown, salient point, sap, scope,
   semantic cluster, semantic field, sense, short, significance,
   signification, significatum, signifie, sine qua non, soul,
   span of meaning, spirit, structural meaning, stuff, subject,
   subject matter, subject of thought, substance, substantive point,
   sum, sum and substance, summary, summation, symbolic meaning,
   tenor, text, the bottom line, the nitty-gritty, the point, theme,
   thrust, topic, totality of associations, transferred meaning,
   turning point, unadorned meaning, undertone, upshot, value



Bouvier's Law Dictionary, Revised 6th Ed (1856):

GIST, pleading. Gist of the action is the essential ground or object of it,
in point of law, and without which there is no cause of action. Gould on Pl.
c. 4, Sec. 12. But it is observable that the substance or gist of the action
is not always the principal cause of the plaintiff Is complaint in point of
fact, nor that on which he recovers all or the greatest part of his damages.
     2. It frequently happens that upon that part of his declaration which
contains the substance or gist of the, action, he only recovers nominal
damages, and he gets his principal satisfaction on account of matter
altogether collateral thereto. A familiar instance of this is the case where
a father sues the defendant for a trespass for the seduction of his
daughter. The gist of the action is the trespass, and the loss of his
daughter's services, but the collateral cause is the injury done to his
feelings, for which the principal damages are given. In stating the
substance or gist of the action, every thing must be averred which is
necessary to be proved at the trial. Vide 1 Vin. Ab. 598; 2 Phil. Ev. 1,
note. See Bac. Abr. Pleas, B; Doct. P. 85. See Damages, special, in
pleading; 1 Vin. At. 598; 2 Phil. Ev. 1, n.