s.v. (Latin: sub voce or sub verbo, meaning ‘under the word/heading’

Definition: (In textual references) under the given word or heading

Beijer Dictionary lists ‘rural policeman’ s.v. ‘rural’

Encyclopedias are generally not cited in bibliographic and footnote formats. However, given our demands at IMSA that students cite sources, the convention below should be followed for encyclopedias. The "s.v." before the word means "sub verbo" (meaning "under the word" or "under the heading").
 
Encyclopedia where there is no author of the entry:
Encyclopedia of World Explorers, 1st ed., s.v. "Samuel de Champlain."

(CHICAGO STYLE GUIDE for IMSA Students)