›[T]to write or type information on a document in spaces that are provided for it: Companies will encourage customers to fill in questionnaires about themselves.Please print off a copy of the agreement, fill it in, sign it and send it back.
›[I]to do the work of someone else for a short time: fill in for sbI asked Agnes to fill in for me while I went for lunch.When you're off sick, someone else has to fill in.
›[T]to tell someone something they do not know, especially something that happened when they were not there: I haven't seen the latest report, so perhaps you could fill me in?fill sb in on sthJosh filled me in on what had been agreed at the meeting.