The Collaborative International Dictionary of English v.0.48:

Sad \Sad\, v. t.
   To make sorrowful; to sadden. [Obs.]
   [1913 Webster]

         How it sadded the minister's spirits!    --H. Peters.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

SAD \SAD\, n.
   Seasonal affective disorder. [Acron.]
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Sad \Sad\ (s[a^]d), a. [Compar. Sadder (s[a^]d"d[~e]r);
   superl. Saddest.] [OE. sad sated, tired, satisfied, firm,
   steadfast, AS. saed satisfied, sated; akin to D. zat, OS.
   sad, G. satt, OHG. sat, Icel. sa[eth]r, saddr, Goth.
   sa[thorn]s, Lith. sotus, L. sat, satis, enough, satur sated,
   Gr. 'a`menai to satiate, 'a`dnh enough. Cf. Assets, Sate,
   Satiate, Satisfy, Satire.]
   1. Sated; satisfied; weary; tired. [Obs.]
      [1913 Webster]

            Yet of that art they can not waxen sad,
            For unto them it is a bitter sweet.   --Chaucer.
      [1913 Webster]

   2. Heavy; weighty; ponderous; close; hard. [Obs., except in a
      few phrases; as, sad bread.]
      [1913 Webster]

            His hand, more sad than lump of lead. --Spenser.
      [1913 Webster]

            Chalky lands are naturally cold and sad. --Mortimer.
      [1913 Webster]

   3. Dull; grave; dark; somber; -- said of colors. "Sad-colored
      clothes." --Walton.
      [1913 Webster]

            Woad, or wade, is used by the dyers to lay the
            foundation of all sad colors.         --Mortimer.
      [1913 Webster]

   4. Serious; grave; sober; steadfast; not light or frivolous.
      [Obs.] "Ripe and sad courage." --Chaucer.
      [1913 Webster]

            Lady Catharine, a sad and religious woman. --Bacon.
      [1913 Webster]

            Which treaty was wisely handled by sad and discrete
            counsel of both parties.              --Ld. Berners.
      [1913 Webster]

   5. Affected with grief or unhappiness; cast down with
      affliction; downcast; gloomy; mournful.
      [1913 Webster]

            First were we sad, fearing you would not come;
            Now sadder, that you come so unprovided. --Shak.
      [1913 Webster]

            The angelic guards ascended, mute and sad. --Milton.
      [1913 Webster]

   6. Afflictive; calamitous; causing sorrow; as, a sad
      accident; a sad misfortune.
      [1913 Webster]

   7. Hence, bad; naughty; troublesome; wicked. [Colloq.] "Sad
      tipsy fellows, both of them." --I. Taylor.
      [1913 Webster]

   Note: Sad is sometimes used in the formation of
         self-explaining compounds; as, sad-colored, sad-eyed,
         sad-hearted, sad-looking, and the like.
         [1913 Webster]

   Sad bread, heavy bread. [Scot. & Local, U.S.] --Bartlett.
      [1913 Webster]

   Syn: Sorrowful; mournful; gloomy; dejected; depressed;
        cheerless; downcast; sedate; serious; grave; grievous;
        afflictive; calamitous.
        [1913 Webster]

WordNet (r) 3.0 (2006):

sad
    adj 1: experiencing or showing sorrow or unhappiness; "feeling
           sad because his dog had died"; "Better by far that you
           should forget and smile / Than that you should remember
           and be sad"- Christina Rossetti [ant: glad]
    2: of things that make you feel sad; "sad news"; "she doesn't
       like sad movies"; "it was a very sad story"; "When I am dead,
       my dearest, / Sing no sad songs for me"- Christina Rossetti
    3: bad; unfortunate; "my finances were in a deplorable state";
       "a lamentable decision"; "her clothes were in sad shape"; "a
       sorry state of affairs" [syn: deplorable, distressing,
       lamentable, pitiful, sad, sorry]

Moby Thesaurus II by Grady Ward, 1.0:

307 Moby Thesaurus words for "sad":
   Quaker-colored, abominable, acier, affecting, afflictive,
   anguished, anxious, arrant, ashen, ashy, atrocious, awful,
   badly off, base, beastly, beggarly, beneath contempt, beneath one,
   bitter, blackish, blameworthy, bleak, blue, bored, brutal,
   canescent, cheap, cheerless, cheesy, cinereous, cinerous,
   comfortless, common, contemptible, creamy, crummy, dapple,
   dapple-gray, dappled, dappled-gray, dark, dark-colored, darkish,
   darksome, debasing, degrading, dejected, delicate, demeaning,
   deplorable, depressed, depressing, depressive, desolate,
   despicable, detestable, dingy, dire, discomforting, disgraceful,
   disgusted, disgusting, dismal, dismaying, dispirited, distressful,
   distressing, doleful, dolorific, dolorogenic, dolorous, donsie,
   doomful, dove-colored, dove-gray, down, downbeat, downcast,
   dreadful, drear, dreary, dull, dumpish, dumpy, dusk, dusky, dusty,
   eggshell, egregious, enormous, evil-starred, fatal, fetid, filthy,
   flagrant, flat, fortuneless, foul, fulsome, funereal, funest,
   gaudy, gimcracky, glaucescent, glaucous, gloomy, gloss, grave,
   gray, gray-black, gray-brown, gray-colored, gray-drab, gray-green,
   gray-spotted, gray-toned, gray-white, grayed, grayish, grieving,
   grievous, grim, griseous, grizzle, grizzled, grizzly, gross,
   gutter, hapless, hateful, heavy, heavyhearted, heinous, horrible,
   horrid, humiliating, humiliative, ill off, ill-starred,
   in adverse circumstances, inauspicious, infamous, infra dig,
   infra indignitatem, iridescent, iron-gray, joyless,
   laden with sorrow, lamentable, lead-gray, leaden, light, livid,
   loathsome, long-faced, lousy, luckless, mean, melancholic,
   melancholy, mellow, meretricious, mirthless, miserable, monstrous,
   morose, mother-of-pearl, mournful, mouse-colored, mouse-gray,
   mousy, moving, nacreous, nasty, nauseated, nauseous, nefarious,
   nigrescent, noisome, notorious, obnoxious, odious, offensive,
   ominous, opalescent, oppressed, opprobrious, out of luck,
   outrageous, painful, pale, paltry, pastel, pathetic, patinaed,
   pearl, pearl-gray, pearly, piteous, pitiable, pitiful,
   planet-struck, pleasureless, poignant, poor, prey to malaise,
   quiet, rank, regrettable, repelled, reprehensible, repulsive,
   revolted, rotten, rubbishy, rueful, sad of heart, sad-eyed,
   sad-faced, saddened, saddening, sadhearted, scandalous, schlock,
   scrubby, scruffy, scummy, scurvy, scuzzy, semigloss, shabby,
   shameful, sharp, shocking, shoddy, short of luck, sickened, silver,
   silver-gray, silvered, silvery, simple, slate-colored, slaty,
   smoke-gray, smoky, sober, soft, soft-colored, soft-hued, softened,
   somber, sombrous, sordid, sore, sorrowful, sorry, squalid,
   star-crossed, steel-gray, steely, stone-colored, subdued, subtle,
   suffering angst, swart, swarthy, sweet, taupe, tear-jerking,
   tender, terrible, too bad, touching, trashy, triste, trumpery,
   two-for-a-cent, two-for-a-penny, twopenny, twopenny-halfpenny,
   unbecoming, unblessed, unclean, uncomfortable, underprivileged,
   uneasy, unfortunate, unfulfilled, ungratified, unhappy, unlucky,
   unprosperous, unprovidential, unquiet, unsatisfied,
   unworthy of one, valueless, vile, villainous, weighed upon,
   weighted down, woebegone, woeful, worst, worthless, wretched



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

SAD
       Security Association Database (SA, IPSec)


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

SAD
       Serial Analog Delay


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

Systems Analysis Definition
SAD

    (SAD) The analysis of the role of a proposed
   system and the identification of the requirements that it
   should meet.  SAD is the starting point for system design.
   The term is most commonly used in the context of commercial
   programming, where software developers are often classed as
   either systems analysts or programmers.  The systems
   analysts are responsible for identifying requirements
   (i.e. systems analysis) and producing a design.  The
   programmers are then responsible for implementing it.

   (1996-03-07)