Simple past tense and past participle of master.(verb)
To reach a high level of competency.(verb)
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Use "mastered" in a sentence
"The DVDs were mastered from the original negatives, and the colors are bright and really pop."
"What A.B. Combs has mastered is to create a unique and deep leadership culture."
"The 2001 release contained the re-release trailer, the film in the original 2.21: 1 aspect ratio, digitally re-mastered from the original 70 mm print, and the soundtrack remixed in 5.1 surround sound."