1.  To be obliged; to be necessitated; -- expressing either physical or moral necessity; as, a man must eat for nourishment; we must submit to the laws. [1913 Webster]

2.  To be morally required; to be necessary or essential to a certain quality, character, end, or result; as, he must reconsider the matter; he must have been insane. [1913 Webster]
" The principal verb, if easily supplied by the mind, was formerly often omitted when must was used; as, I must away. “I must to Coventry.” Shak." [1913 Webster]
"Likewise must the deacons be grave." [1913 Webster]
"Morover, he [a bishop] must have a good report of them which are without." [1913 Webster]

1.  The expressed juice of the grape, or other fruit, before fermentation. Wyclif (Acts ii. 13.). [1913 Webster]
"No fermenting must fills . . . the deep vats." [1913 Webster]

2.  Mustiness. [1913 Webster]

   To make musty; to become musty. [1913 Webster]

   Being in a condition of dangerous frenzy, usually connected with sexual excitement; -- said of adult male elephants which become so at irregular intervals, typicaly due to increased testosterone levels. [Webster 1913 Suppl.]

must, v. & n.
--v.aux. (3rd sing. present must; past had to or in indirect speech must) (foll. by infin., or absol.)
1 a be obliged to (you must go to school; must we leave now?; said he must go; I must away).

Idiom:
I must say often iron. I cannot refrain from saying (I must say he made a good attempt; a fine way to behave, I must say). must needs see NEEDS.

Usage:
The negative (i.e. lack of obligation) is expressed by not have to or need not; must not denotes positive forbidding, as in you must not smoke. b in ironic questions (must you slam the door?).
2 be certain to (we must win in the end; you must be her sister; he must be mad; they must have left by now; seemed as if the roof must blow off).
3 ought to (we must see what can be done; it must be said that).
4 expressing insistence (I must ask you to leave).
5 (foll. by not + infin.) a not be permitted to, be forbidden to (you must not smoke). b ought not; need not (you mustn't think he's angry; you must not worry). c expressing insistence that something should not be done (they must not be told).
6 (as past or historic present) expressing the perversity of destiny (what must I do but break my leg).
--n. colloq. a thing that cannot or should not be overlooked or missed (if you go to London St Paul's is a must).

must, n. grape-juice before fermentation is complete.

must, n. mustiness, mould.

must, adj. & n. (also musth)
--adj. (of a male elephant or camel) in a state of frenzy.
--n. this state.

Etymology:
Urdu f. Pers. mast intoxicated

N  uncleanness, impurity, immundity, immundicity, impurity, defilement, contamination, defoedation, soilure, soiliness, abomination, leaven, taint, tainture, fetor, decay, putrescence, putrefaction, corruption, mold, must, mildew, dry rot, mucor, rubigo, slovenry, slovenliness, squalor, dowdy, drab, slut, malkin, slattern, sloven, slammerkin, slammock, slummock, scrub, draggle-tail, mudlark, dust-man, sweep, beast, dirt, filth, soil, slop, dust, cobweb, flue, smoke, soot, smudge, smut, grit, grime, raff, sossle, sozzle, sordes, dregs, grounds, lees, argol, sediment, settlement heeltap, dross, drossiness, mother, precipitate, scoriae, ashes, cinders, recrement, slag, scum, froth, hogwash, ditchwater, dishwater, bilgewater, rinsings, cheeseparings, sweepings, offscourings, outscourings, off scum, caput mortuum, residuum, sprue, fecula, clinker, draff, scurf, scurfiness, exuviae, morphea, fur, furfur, dandruff, tartar, riffraff, vermin, louse, flea, bug, chinch, mud, mire, quagmire, alluvium, silt, sludge, slime, slush, slosh, sposh, spawn, offal, gurry, lientery, garbage, carrion, excreta, slough, peccant humor, pus, matter, suppuration, lienteria, faeces, feces, excrement, ordure, dung, crap, shit, sewage, sewerage, muck, coprolite, guano, manure, compost, dunghill, colluvies, mixen, midden, bog, laystall, sink, privy, jakes, toilet, john, head, cess, cesspool, sump, sough, cloaca, latrines, drain, sewer, common sewer, Cloacina, dust hole, sty, pigsty, lair, den, Augean stable, sink of corruption, slum, rookery, dirty, filthy, grimy, unclean, impure, soiled, not to be handled with kid gloves, dusty, snuffy, smutty, sooty, smoky, thick, turbid, dreggy, slimy, mussy, slovenly, untidy, messy, uncleanly, unkempt, sluttish, dowdy, draggle-tailed, uncombed, unscoured, unswept, unwiped, unwashed, unstrained, unpurified, squalid, lutose, slammocky, slummocky, sozzly, nasty, coarse, foul, offensive, abominable, beastly, reeky, reechy, fetid, decayed, moldy, musty, mildewed, rusty, moth-eaten, mucid, rancid, weak, bad, gone bad, etercoral, lentiginous, touched, fusty, effete, reasty, rotten, corrupt, tainted, high, flyblown, maggoty, putrid, putrefactive, putrescent, putrefied, saprogenic, saprogenous, purulent, carious, peccant, fecal, feculent, stercoraceous, excrementitious, scurfy, scurvy, impetiginous, gory, bloody, rotting, rotten as a pear, rotten as cheese, crapulous, gross, fimetarious, fimicolous, they that touch pitch will be defiled.

N  impurity, uncleanness, immodesty, grossness, indelicacy, indecency, impudicity, obscenity, ribaldry, Fescennine, smut, bawdry, double entente, equivoque, concupiscence, lust, carnality, flesh, salacity, pruriency, lechery, lasciviency, lubricity, Sadism, sapphism, incontinence, intrigue, faux pas, amour, amourette, gallantry, debauchery, libertinish, libertinage, fornication, liaison, wenching, venery, dissipation, seduction, defloration, defilement, abuse, violation, rape, incest, prostitution, social evil, harlotry, stupration, whoredom, concubinage, cuckoldom, adultery, advoutry, crim, con, free love, seraglio, harem, brothel, bagnio, stew, bawdyhouse, cat house, lupanar, house of ill fame, bordel, bordello, impure, unclean, not to be mentioned to ears polite, immodest, shameless, indecorous, indelicate, indecent, Fescennine, loose, risque, coarse, gross, broad, free, equivocal, smutty, fulsome, ribald, obscene, bawdy, pornographic, concupiscent, prurient, lickerish, rampant, lustful, carnal, carnal-minded, lewd, lascivious, lecherous, libidinous, erotic, ruttish, salacious, Paphian, voluptuous, goatish, must, musty, unchaste, light, wanton, licentious, debauched, dissolute, of loose character, of easy virtue, frail, gay, riggish, incontinent, meretricious, rakish, gallant, dissipated, no better than she should be, on the town, on the streets, on the pave, on the loose, adulterous, incestuous, bestial.