Open and sincere in expression; straightforward: made several frank remarks about the quality of their work.
Clearly manifest; evident: frank enjoyment.
tr.v.
franked, frank·ing, franks
To put an official mark on (a piece of mail) so that it can be sent free of charge.
To send (mail) free of charge.
To place a stamp or mark on (a piece of mail) to show the payment of postage.
To enable (a person) to come and go freely.
n.
A mark or signature placed on a piece of mail to indicate the right to send it free of charge.
The right to send mail free.
A franked piece of mail.
[Middle English, free, from Old French franc, from Late Latin Francus, Frank; see Frank.] frank'ness n.
Synonyms: These adjectives mean revealing or disposed to reveal one's thoughts freely and honestly. Frank implies forthrightness, sometimes to the point of bluntness: "Be calm and frank, and confess at once all that weighs on your heart" (Emily Brontë). Candid often suggests refusal to evade difficult or unpleasant issues: "Save, save, oh save me from the candid friend!" (George Canning). Outspoken usually implies bold lack of reserve: The outspoken activist protested the budget cuts. Straightforward denotes directness of manner and expression: "George was a straightforward soul....'See here!' he said. 'Are you engaged to anybody?'" (Booth Tarkington). Open suggests freedom from all trace of reserve or secretiveness: "I will be open and sincere with you" (Joseph Addison).
[frangk-nis] 
nɪs