Source : Webster's Revised Unabridged Dictionary (1913)

Footnote \Foot"note`\, n.
   A note of reference or comment at the foot of a page.

Source : WordNet®

footnote
     n : a printed note placed below the text on a printed page [syn:
          {footer}]
     v : add explanatory notes to or supply with critical comments;
         "The scholar annotated the early edition of a famous
         novel" [syn: {annotate}]