Without proper nouns, names etc
Pneumonoultramicroscopicsilicovolcanocon... is, according to the Oxford English Dictionary, "a word alleged to mean 'a lung disease caused by the inhalation of volcanic ash, causing inflammation in the lungs.'"
Source(s):
http://en.wikipedia.org/wiki/Longest_wor...
The longest word not in the dictionary is:
• This is the chemical name of the largest known protein. It is an astonishing 189,819 letters long. However it is purely a technical term and though written in English it isn't a "dictionary" term and thus the first answerer is the most correct.
Methionylthreonylthreonylglutaminylala... ylglutaminylprolylleucylglutaminylsery... lserylthreonylalanylthreonylphenylalan... rylglycylphenylalanylprolylvalylprolyl... lanylarginylaspartylglycylglutaminylva... nylleucylprolylglycylvalylglutaminylis... ylglycylarginylalanyllysylleucylthreon... llysylalanylasparaginylserylglycylargi... eonylasparaginylglycylserylglycylgluta... nylglutamylleucylleucylvalyllysylalany... asparaginylphenylalanylvalylglutaminyl... ylthreonylvalylarginylglutaminylglycyl... utaminylvalylarginylvalylthreonylglycy... lylvalyllysylphenylalanyltyrosylarginy... cylglutaminylserylserylleucylaspartylp... glutaminylglutamylglycylaspartylleucyl... anylglutamylalanyltyrosylprolylglutamy... serylvalylasparaginylalanylthreonylasp... ylthreonylserylthreonylalanylglutamyll... tamylglutamylglutamylvalylprolylalanyl... eucylvalylserylthreonylalanylglutaminy... glutaminylthreonylarginylisoleucylglut... ylhistidylphenylalanylaspartylalanylar... lylglutamylmethionylvalylisoleucylaspa... nylglutaminylleucylprolylhistidyllysyl... lprolylprolyllysylprolyllysylserylargi... erylisoleucylalanylalanyllysylalanylgl... ylglutaminylserylprolylserylprolylisol... lprolylvalylarginylhistidylvalylarginy... lylvalylarginylserylvalylserylprolylal... onylserylprolylisoleucylarginylserylva... thionylarginyllysylthreonylglutaminyla... ylglycylprolylglutamylvalylprolylproly... tamylglycyltyrosylvalylalanylserylsery... ylarginylglutamylthreonylthreonylleucy... minylisoleucylarginylthreonylglutamylg... cylarginyltyrosylglycylvalylglutaminyl... eucylserylglycylalanylalanylglycylalan... serylalanylseryltyrosylalanylalanylglu... lalanyllysylglutamylvalyllysylglutamin... lanylalanylvalylalanylthreonylvalylval... lalanylarginylvalylarginylglutamylprol... tamylglutaminylthreonylalanylglutaminy... eonylalanylvalylhistidylisoleucylgluta... glutaminylvalylarginyllysylglutamylala... threonyllysylvalylvalylvalylalanylalan... lutaminylglutamylleucyllysylserylargin... leucylthreonylthreonyllysylglutaminylg... alylthreonylhistidylglutamylglutaminyl... ylglutamyllysylthreonylphenylalanylval... ylalanylalanyllysylalanyllysylglutamyl... oleucylserylglutamylglutamylisoleucylt... taminylvalylthreonylglutaminylglutamyl... ylthreonylarginyllysylthreonylvalylval... nylthreonylprolyllysylvalyllysylglutam... larginylglycylarginylglutamylglycyliso... lutamylglutaminylvalylglutaminylisoleu... ethionylarginyllysylglutamylalanylglut... hreonylisoleucylalanylvalylalanylthreo... utaminylglutamylthreonylisoleucylleucy... onylmethionylalanylthreonylarginylglut... utaminylvalylthreonylhistidylglycyllys... lalanylglutamylalanylvalylalanylthreon...