Definition of online in US English:

online

adjective

Computing
  • 1Controlled by or connected to another computer or to a network.

    • ‘Still, only thirty-one computers were online - that is connected to each other - in 1960.’
    • ‘After the thirty seconds, the system would be completely back online and the IMX network would again run for a full year.’
    1. 1.1 Connected to the Internet or World Wide Web.
      ‘the ease and convenience of online shopping’
      • ‘Also available is an online shopping service that lists recommended foods based on a person's medical history.’
      • ‘They also say they are more interested in the Internet for online entertainment than other users, according to the study.’
      • ‘Godfrey has also sued several other Internet service providers and online publications.’
      • ‘The free online service is available on the Joburg City website, under e-services.’
      • ‘You can find more information about online education on the internet.’

adverb

Computing
  • 1While so connected or under computer control.

    • ‘Moments later the flight control system came online, my HUD flickering into life.’
    • ‘Once inside, the controls came online as he flicked on a few switches.’
    • ‘Security controls had been back online as well as the little traps they planted through the space station.’
    1. 1.1 With processing of data carried out simultaneously with its production.
  • 2In or into operation or existence.

    ‘the town's new high-tech power plant is expected to go online this month’
    ‘the company has additional production capacity coming online later this year’
    • ‘The legwork has been taken out of the planning procedure by a Yorkshire council which has become one of the first authorities in Britain to put the whole process online.’
    • ‘If all goes well, Munton said construction could begin as early as September, with a fully operational plant online in about a year.’
    • ‘Now that we have reminded them, we expect it to be online shortly.’
    • ‘Air National Guard offices are expected to go online in July.’
    • ‘The new facility came online this month and expects to ramp up to full production by March.’

Pronunciation

online

/änˈlīn//ɑnˈlaɪn/