Merriam-Webster's Word of the Day for July 29, 2010 is:

adjure • \uh-JOOR\  • verb
1 : to command solemnly under or as if under oath or penalty of a curse *2 : to urge or advise earnestly

Example sentence:
"Byron fled the country, adjuring Annabella to 'be kind' to his beloved sister." (Merle Rubin, Los Angeles Times, September 16, 2002)

Did you know?
"Adjure" and its synonyms "entreat," "importune," and "implore" all mean "to ask earnestly." "Entreat" implies an effort to persuade or overcome resistance. "Importune" goes further, adding a sense of annoying persistence in trying to break down resistance to a request. "Implore," on the other hand, suggests a great urgency or anguished appeal on the part of the speaker. "Adjure" implies advising as well as pleading, and is sometimes accompanied by the invocation of something sacred. Be careful not to confuse "adjure" with "abjure," meaning "to renounce solemnly" or "to abstain from." Both words are rooted in Latin "jurare," meaning "to swear," but "adjure" includes the prefix "ad-," meaning "to" or "toward," whereas "abjure" draws on "ab-," meaning "from" or "away."

*Indicates the sense illustrated in the example sentence.