Different dictionaries defines News differently. But there are some commonness among those descriptions. Here are some definitions from widely used dictionaries:

Dictionary of Canadian English
•    something told as having just happened: information about something that has just happened or will soon happen
•    a report of a current happening or happenings in a newspaper, on television, radio, etc.

Random House Dictionary
•    a report of a current event
•    a report on current events in a newspaper or on radio or television
•    such reports taken collectively
•    a report of a recent event; information
•    a report on recent or new events in a newspaper or other periodical or on radio or television
•    such reports taken collectively; information reported
•    a person, event, etc., regarded as newsworthy material

American Heritage Dictionary
•    recent events and happenings
•    a report about recent events
•    new information
•    information about recent events or happenings, especially as reported by means of newspapers, websites, radio, television, and other forms of media
•    a presentation of such information, as in a newspaper or on a newscast
•    newsworthy material
•    new information, especially about recent events and happenings
•    something significant that happens

Oxford Shorter Dictionary
•    new things, novelties
•    tidings, new information of recent events; new occurrences as a subject of report or talk
•    a newspaper

Cambridge English Dictionary
•    information or reports about recent events
•    a television or radio programme consisting of reports about recent events
•    to tell someone about something bad that has just happened and may have an effect on them
•    to be someone or something that will affect a person or situation well/badly
•    to be reported about

Merriam-Webster Dictionary
•    a report of recent events
•    previously unknown information
•    something having a specified influence or effect
•    material reported in a newspaper or news periodical or on a newscast listened to the news on the radio
•    matter that is newsworthy
•    newscast

Collins English Dictionary
•    news is information about a recently changed situation or a recent event
•    news is information that is published in newspapers and broadcast on radio and television about recent events in the country or world or in a particular area of activity
•    the news is a television or radio broadcast which consists of information about recent events in the country or the world
•    current events; important or interesting recent happenings
•    information about such events, as in the mass media
•    a presentation, such as a radio broadcast, of information of this type
•    interesting or important information not previously known or realized

Collins COBUILD English Usage Dictionary
•    news is information about a recent event or a recently changed situation
•    a description of an event on television or in a newspaper is a news item or an item of news

Globe Modern Dictionary
•    a report of events as given each day by newspaper, radio, etc.
•    information which was not known before

Wikipedia
•    news is information about current events

Wikitionary
•    new information of interest
•    information about current events disseminated via media
•    posts published on newsgroups

Farlex Trivia Dictionary
•    report – to report something is etymologically to “carry it back”, from Latin reportare; the metaphorical sense of “bringing back news” also developed in Latin