Source : Webster's Revised Unabridged Dictionary (1913)

January \Jan"u*a*ry\, n. [L. Januarius, fr. Janus an old Latin
   deity, the god of the sun and the year, to whom the month of
   January was sacred; cf. janua a door, Skr. y[=a] to go.]
   The first month of the year, containing thirty-one days.

   Note: Before the adoption of New Style, the commencement of
         the year was usually reckoned from March 25.

Source : WordNet®

January
     n : the first month of the year; begins 10 days after the winter
         solstice [syn: {Jan}]