'X-ray tube' definitions:

Definition of 'X-ray tube'

From: WordNet
noun
A vacuum tube containing a metal target onto which a beam of electrons is directed at high energy for the generation of X rays

Definition of 'X-ray tube'

From: GCIDE
  • X-ray tube \X"-ray` tube\ (Physics) A vacuum tube suitable for producing Roentgen rays. [Webster 1913 Suppl.]