Source : Webster's Revised Unabridged Dictionary (1913)

Monday \Mon"day\ (m[u^]n"d[asl]; 48), n. [OE. moneday, monenday,
   AS. m[=o]nand[ae]g, i.e., day of the moon, day sacred to the
   moon; akin to D. maandag, G. montag, OHG. m[=a]natag, Icel.
   m[=a]nadagr, Dan. mandag, Sw. m[*a]ndag. See {Moon}, and
   {Day}.]
   The second day of the week; the day following Sunday.

Source : WordNet®

Monday
     n : the second day of the week; the first working day [syn: {Mon}]