What's the correct format of a footnote for a term definition which came from a website?

For example,





Ubiquitous - seemingly present everywhere





What's a correct format of a footnote that shows the word ';Ubiquitous'; came from encarta.msn.com?What's the correct format of a footnote for a term definition which came from a website?
why are you footnoting a word? this doesn't really make sense.





also, most instructors would rather see you cite to a paper dictionary, even if encarta is actually where you learned the word.