Definition of "fill in"

fill in

verb
third-person singular simple present fills in, present participle filling in, simple past and past participle filled in
1. (transitive) To fill; to replace material that is absent or has been removed.
  Quotations
  Typically for the 'get-on-with-it' era, the railway and military worked like demons to restore the vital rail link. The crater was rapidly filled in and the earth tamped solid, the wreckage was removed by breakdown trains, new rails and sleepers were rushed forward by willing hands, and US Army bulldozers piled in. By 2020 on the same day, both tracks were open for traffic again where there had been a gaping pit just hours before.
  2022 January 12, Benedict le Vay, “The heroes of Soham...”, in RAIL, number 948, page 43
2. (transitive, idiomatic) To inform somebody, especially to supply someone missing or missed information.
3. (intransitive, idiomatic) To substitute for somebody or something.
4. (transitive, chiefly Britain) To complete a form or questionnaire with requested information.
  Quotations
  The findings emerged from questionnaires filled in by 2,211 staff in 145 wards of 55 hospitals in England and Wales and 105 observations of care of dementia patients. Two-thirds of staff said they had not had enough training to provide proper care, 50% said they had not been trained how to communicate properly with such patients and 54% had not been told how to handle challenging or aggressive behaviour.
  2011 December 16, Denis Campbell, “Hospital staff 'lack skills to cope with dementia patients'”, in Guardian‎
5. (slang) To beat up; to physically assault.
  Quotations
  It's just a rumour that was spread around townSomebody said that someone got filled inFor saying that people get killed inThe result of this shipbuilding
  1982, Elvis Costello, Shipbuilding