Simple past tense and past participle of letterbox.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "letterboxed" in a sentence
"( 'letterboxed') or cropped to a 4: 3 frame, otherwise your showreel will be distorted by the encoding process."
"Regular 35mm upconverts like “Star Trek” have the letterboxed look throughout the entire movie."
"But then I've loved all the Justice Leagues (well except for those crappy NON-anamorphic, letterboxed dvds that Warner put out: P) seandps has anyone had any luck finding the 12.99 blu ray titles at Target?"