words whose meaning that have downgraded?
446586
hussy--originally housewife (huswif)\nsilly--originally holy (related to German selig)\nDowngraded is probably not the correct term.  Words simply change their meaning over the years.
453484
cool, crazy, daffy, dippy, dizzy, flaky, fool, fool around, foolish, for grins, freaked out, freaky, gagged up, goofy, idiotic, illogical, inane, incongruous, irrational nonsensical, jokey, joshing, kooky, laughable, loony, ludicrous, monkey, nutty, preposterous, sappy, screwy, senseless, shtick, silly, stupid, tomfool, unreasonable, wacky...
212934
egoistic, egoistical, egomaniacal, egotistic, egotistical, individualist, individualistic, megalomaniac, narcissistic, pompous, self-absorbed, self-centered, self-concerned, self-indulgent, self-interested, self-loving, self-serving, selfish, stuck-up, vainglorious
656539
Colour, favourite, darby (instead of derby), serviette instead of napkin, defence instead of defense.\n\n"I beg your pardon." instead of "What?"\n\nRead some English literature to help you.
1130513
DOWN\n5 - another word for strange (5 letters)\n\nWEIRD
636300
AEQUORIN, AEROBIUM, AGOUTIES, DIALOGUE, EDACIOUS, EQUATION, EULOGIAS, EUPHORIA, EUSOCIAL, EXONUMIA, JALOUSIE, OUTRAISE, SAUTOIRE, SEQUOIAS, and THIOUREA
567394
the only ones i can think of are words that change slightly.... \n\nprinces - plural\nprincess - singular\n\nbut the meaning is a little different, lol. does that count?
939610
Bashed, befuddled, boozed up, buzzed, canned, crocked, drinking, drunken, flushed, flying, fuddled, gassed, glazed, groggy, hammered, high, hosed, in orbit, inebriated, jolly, jugged, juiced, laced, liquored up, lit, lush, merry, muddled, oiled, on a bun, overcome, pie-eyed, plastered, plowed, potted, seeing double, sloshed, soaked, sotted, soused, stewed, tanked, three sheets to the wind, tight, tipsy, totaled, trashed, wasted, worshipping the porcelain god, zonked.
697607
Dirty\nLazy\nWimps\nBitchy\nCowards
515037
corrupt..\nSudan\nBangladesh\nfavourite..\nNorway
402145
Betray. \n\nabandon, bluff, break faith, break promise, break trust, break with, commit treason, cross, delude, desert, double-cross, forsake,  let down.\n\nThere is really not a word with that exact meaning.
201896
go to \n://encarta.msn.com/encnet/features/dictionary/dictionaryhome.aspx\nor use microsoft word and right click and go to synonyms
445189
The ones I found were\nexamination\nexploration\ninquiry\ninvestigation\nscrutiny\nstudy
199570
The F word is Anglo Saxon.  Most others are corruptions of body parts.  My favourite is my old grandad's: 'Bad cess to you'.   It took me a long time to figure it out, but the cess is as in cesspit.
99551
Actually it means shamed,disgraced or humiliated
270820
Desenselessness\n\nAnother one : Defenselessness
923748
Yes, there are several (So-called Reverse Dictionaries). My favorite is:\n\nhttp://www.onelook.com/reverse-dictionary.sh