1.  sac(n = noun.shape) pocket, pouch, sack - an enclosed space; "the trapped miners found a pocket of air"
is a kind of cavity, enclosed space

2.  sac(n = noun.plant) theca - a case or sheath especially a pollen sac or moss capsule;
is a kind of cover, covering, natural covering

3.  sac(n = noun.person) sauk - a member of the Algonquian people formerly living in Wisconsin in the Fox River valley and on the shores of Green Bay;
is a kind of algonquian, algonquin
has particulars: black hawk, makataimeshekiakiak, keokuk

4.  sac(n = noun.body) - a structure resembling a bag in an animal;
is a kind of bodily cavity, cavity, cavum
has particulars: yolk sac, umbilical vesicle, vesicula umbilicus, vitelline sac, yolk sac, amnion, amnios, amniotic sac, chorion, coelenteron, air bladder, float, swim bladder, air sac, air sac, saccule, sacculus, bladder, vesica, acinus, bursa, cistern, cisterna, pocket, pouch, cyst, vesicle, air cell, air sac, alveolus, pericardial sac

   See Sacs. [1913 Webster]

   The privilege formerly enjoyed by the lord of a manor, of holding courts, trying causes, and imposing fines. Cowell. [1913 Webster]

1.  See 2d Sack. [1913 Webster]

2.  A cavity, bag, or receptacle, usually containing fluid, and either closed, or opening into another cavity to the exterior; a sack. [1913 Webster]

sac, abbr. (in the UK) Senior Aircraftman.

sac, n.
1 a baglike cavity, enclosed by a membrane, in an animal or plant.
2 the distended membrane surrounding a hernia, cyst, tumour, etc.

Etymology:
F sac or L saccus SACK(1)

N  receptacle, inclosure, recipient, receiver, reservatory, compartment, cell, cellule, follicle, hole, corner, niche, recess, nook, crypt, stall, pigeonhole, cove, oriel, cave, capsule, vesicle, cyst, pod, calyx, cancelli, utricle, bladder, pericarp, udder, stomach, paunch, venter, ventricle, crop, craw, maw, gizzard, breadbasket, mouth, pocket, pouch, fob, sheath, scabbard, socket, bag, sac, sack, saccule, wallet, cardcase, scrip, poke, knit, knapsack, haversack, sachel, satchel, reticule, budget, net, ditty bag, ditty box, housewife, hussif, saddlebags, portfolio, quiver, chest, box, coffer, caddy, case, casket, pyx, pix, caisson, desk, bureau, reliquary, trunk, portmanteau, band-box, valise, grip, grip sack, skippet, vasculum, boot, imperial, vache, cage, manger, rack, vessel, vase, bushel, barrel, canister, jar, pottle, basket, pannier, buck-basket, hopper, maund, creel, cran, crate, cradle, bassinet, wisket, whisket, jardiniere, corbeille, hamper, dosser, dorser, tray, hod, scuttle, utensil, brazier, cuspidor, spittoon, cistern, vat, caldron, barrel, cask, drum, puncheon, keg, rundlet, tun, butt, cag, firkin, kilderkin, carboy, amphora, bottle, jar, decanter, ewer, cruse, caraffe, crock, kit, canteen, flagon, demijohn, flask, flasket, stoup, noggin, vial, phial, cruet, caster, urn, epergne, salver, patella, tazza, patera, pig gin, big gin, tyg, nipperkin, pocket pistol, tub, bucket, pail, skeel, pot, tankard, jug, pitcher, mug, pipkin, galipot, gallipot, matrass, receiver, retort, alembic, bolthead, capsule, can, kettle, bowl, basin, jorum, punch bowl, cup, goblet, chalice, tumbler, glass, rummer, horn, saucepan, skillet, posnet, tureen, beaker, flask, Erlenmeyer flask, Florence flask, round-bottom flask, graduated cylinder, test tube, culture tube, pipette, Pasteur pipette, disposable pipette, syringe, vial, carboy, vacuum flask, Petri dish, microtiter tray, centrifuge tube, bail, beaker, billy, canakin, catch basin, catch drain, chatti, lota, mussuk, schooner, spider, terrine, toby, urceus, plate, platter, dish, trencher, calabash, porringer, potager, saucer, pan, crucible, glassware, tableware, vitrics, compote, gravy boat, creamer, sugar bowl, butter dish, mug, pitcher, punch bowl, chafing dish, shovel, trowel, spoon, spatula, ladle, dipper, tablespoon, watch glass, thimble, closet, commode, cupboard, cellaret, chiffonniere, locker, bin, bunker, buffet, press, clothespress, safe, sideboard, drawer, chest of drawers, chest on chest, highboy, lowboy, till, scrutoire, secretary, secretaire, davenport, bookcase, cabinet, canterbury, escritoire, etagere, vargueno, vitrine, chamber, apartment, room, cabin, office, court, hall, atrium, suite of rooms, apartment, flat, story, saloon, salon, parlor, by-room, cubicle, presence chamber, sitting room, best room, keeping room, drawing room, reception room, state room, gallery, cabinet, closet, pew, box, boudoir, adytum, sanctum, bedroom, dormitory, refectory, dining room, salle-a-manger, nursery, schoolroom, library, study, studio, billiard room, smoking room, den, stateroom, tablinum, tenement, bath room, bathroom, toilet, lavatory, powder room, john, jakes, necessary, loo, men's room, ladies' room, rest room, (uncleanness), 653 attic, loft, garret, cockloft, clerestory, cellar, vault, hold, cockpit, cubbyhole, cook house, entre-sol, mezzanine floor, ground floor, rez-de-chaussee, basement, kitchen, pantry, bawarchi-khana, scullery, offices, storeroom, lumber room, dairy, laundry, coach house, garage, hangar, outhouse, penthouse, lean-to, portico, porch, stoop, stope, veranda, patio, lanai, terrace, deck, lobby, court, courtyard, hall, vestibule, corridor, passage, breezeway, ante room, ante chamber, lounge, piazza, veranda, conservatory, greenhouse, bower, arbor, summerhouse, alcove, grotto, hermitage, lodging, bed, carriage, capsular, saccular, sacculated, recipient, ventricular, cystic, vascular, vesicular, cellular, camerated, locular, multilocular, polygastric, marsupial, siliquose, siliquous.

air sac, amniotic sac, cul de sac, embryo sac, greater peritoneal sac, lacrimal sac, pericardial sac, sac fungus, spore sac, tear sac, vitelline sac, yolk sac