- (uncountable) The space that something occupies.
- (countable & uncountable) Extension is the process of making something longer.
- (countable) An extension is the time or part of something that was added to make it longer.
- She had extensions put in her hair and now she has long hair.
- He couldn't pay in May so the bank gave him an extension until July.
- (countable & uncountable) An extension is the operation of pulling the two ends of a broken bone to bring the broken pieces into the same straight line.
- (countable & uncountable) Extension is the act of moving an arm, leg, finger, etc. so that it is straight.