English:
Pneumonoultramicroscopicsilicovocanpconisosis (a lung disease caused by breathing in particles of siliceous volcanic dust)

French:
Anticonstitutionnellement (in an unconstitutional way)

Spanish:
Hexakosioihexekontahexafobia (fear of the number 666)

German:
Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz (cattle marking and beef labeling supervision duties delegation law)

Dutch:
Kindercarnavalsoptochtvoorbereidingswerkzaamheden (preparation activities for a children’s carnival procession)

Hungarian:
Megszentségteleníthetetlenségeskedéseitekért (for your unprofaneable actions). What makes it really special is that it derives from a monosyllabic stem ‘szent’ meaning ‘saint’, all the rest is affixes!

Czech:
Nejnerestrukturalizovávatelnějšími (the less farmed / the most ‘unrestructable’ -in instrumental case-)

Polish:
Konstantynopolitańczykowianeczka (a girl living in Constantinople)

Russian:
Тетрагидропиранилциклопентилтетрагидропиридопиридиновые (chemical substance)

Croatian:
Prijestolonaslijednikovica (the wife of a heir to the throne)

Slovenian:
Dialektičnomaterialističen (dialectical materialistic)

Italian:
Psiconeuroendocrinoimmunologia (a discipline that deals with the relationship between the functioning of the nervous system, the immune system and the endocrine system)

Modern Greek:
ακτινοχρυσοφαιδροβροντολαμπροφεγγοφωτοστόλιστος (dressed in golden-shining, thundering and incandescent clothes)

Turkish:
Muvaffakiyetsizlestiricilestiriveremeyebileceklerimizdenmissinizcesine (as if you would be from those we can not easily/quickly make a maker of unsuccessful ones)

Bulgarian:
Непротивоконституционствувателствувайте (do not perform actions against constitution)

Latvian:
Pretpulksteņrādītājvirziens (in a counter-clockwise direction)

Lithuanian:
Nebeprisikiškiakopūsteliaudavusiems (for those who were repeatedly unable to pick enough wood-sorrel leaves / rabbit cabbage in the past)

Danish:
Speciallægepraksisplanlægningsstabiliseringsperiode (period where a specialist doctors planning of the practice is stabilised)

Finnish:
Lentokonesuihkuturbiinimoottoriapumekaanikkoaliupseerioppilas (technical warrant officer trainee specialized in aircraft jet engines)

Swedish:
Nordvästersjökustartilleriflygspaningssimulatoranläggningsmaterielunderhållsuppföljningssystemdiskussionsinläggsförberedelsearbeten (north west sea coastal artillery reconnaissance flight simulator facility equipment maintenance follow-up discussion posts preparatory work)

Norwegian:
Dampskipsundervannsstyrkeprøvemaskinerikonstruksjonsvanskeligheter (steamship underwater strength test machinery construction difficulties)

Icelandic:
Vaðlaheiðarvegavinnuverkfærageymsluskúraútidyralyklakippuhringur (Key ring of the key chain of the outer door to the storage tool shed of the road workers on the Vaðlaheiði plateau)

Gaelic:
Grianghrafadóireachta (photographer)

Welsh:
Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogoch (name of a small town north of the country, literal meaning: St Mary’s in Hollow of the White Hazel near to the Rapid Whirlpool of Llantysilio of the Red Cave)

Afrikaans:
Tweedehandsemotorverkoopsmannevakbondstakingsvergaderingsameroeperstoespraakskrywerspersverklaringuitreikingsmediakonferensieaankondiging (issuable media conference’s announcement at a press release regarding the convener’s speech at a secondhand car dealership union’s strike meeting)

Hebrew:
וכשלאנציקלופדיותינו (and when our encyclopedias)

Korean:
청자양인각연당초상감모란문은구대접 (a kind of ceramic bowl from the Goryeo dynasty)

Vietnamese:
Nghiêng (inclined)

Latin:
Honorificabilitudinitatibus (the state of being able to achieve honours)

AncientGreek:
λοπαδο­τεμαχο­σελαχο­γαλεο­κρανιο­λειψανο­δριμ­υπο­τριμματο­σιλφιο­καραβο­μελιτο­κατακεχυ­μενο­κιχλ­επι­κοσσυφο­φαττο­περιστερ­αλεκτρυον­οπτο­κεφαλλιο­κιγκλο­πελειο­λαγῳο­σιραιο­βαφη­τραγανο­πτερύγων (a recipe with many different ingrédients, dainties, fish, fowl and sauces, invented by Aristophanes in the antiquity) 172 letters! The longest word in the entire world according to Guinness Records.