This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. Device or marking such as postage stamp, printed or stamped impressions, codings, labels, manuscript writings, or any other authorized form of markings affixed or applied to mails to qualify them to be postally serviced.

v. Present participle of frank.

n. A method of forming a joint at the intersection of window-sash bars, by cutting away only enough wood to show a miter.

"Well, for one thing, the always helpful Wikipedia tells us that the very word franking comes from the Latin word "francus," meaning free."

frank   

Nanking    banking    blanking    clanking    cranking