cable box

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An electronic tuning device, often including a descrambler, that allows channels transmitted by cable to be selected for viewing on a television.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun television set top box connecting a house to its cable service.
• noun television A device given out by some cable television services that allows the user to have more channels on their television than they would have without the cable box.
• noun television A descrambler used to descramble scrambled television channels on cable TV