Source : Webster's Revised Unabridged Dictionary (1913)

Inauguration Day \In*au`gu*ra"tion Day\
   The day on which the President of the United States is
   inaugurated, the 4th of March in every year next after a year
   divisible by four.

Source : WordNet®

Inauguration Day
     n : the day designated for inauguration of the United States
         president [syn: {January 20}]