home Josh Murfitt extension ex⋅ten⋅sion [ik-sten-shuhn] –noun 1. an act or instance of extending. 2. the state of being extended. 3. that by which something is extended; an addition: a four-room extension to a house. 4. an additional period of time given one to meet an obligation: My term paper wasn't finished so I asked for an extension. 5. something that can be extended; an extended object: a table with drop-leaf extensions. 6. range of extending; degree of extensiveness; extent: the extension of our knowledge. 7. an additional telephone that operates on the principal line. e a b c d e f g h i j k l m n o p q r s t u v w x y z epiphany ephemeral eventuality error exhausted equilibrium extension