It is a morbid craving for alcohol.
Albert Day has written: 'Methomania; a treatise on alcoholic poisoning' -- subject(s): Alcoholism
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 17 words with the pattern -----M-N-A. That is, ten letter words with 6th letter M and 8th letter N and 10th letter A. In alphabetical order, they are: anglomania anthomania barramunda dipsomania erotomania eudaemonia excrementa hydromania hypermania leishmania methomania metromania mythomania necromania nostomania phagomania tridominia