fill in meaning and definition

FILL IN verb

Definition of fill in (verb)

1. supply with information on a specific topic
   • "He filled me in on the latest developments"
2. represent the effect of shade or shadow on
   • synonyms: shade
3. be a substitute
   • "The young teacher had to substitute for the sick colleague"; "The skim milk substitutes for cream--we are on a strict diet"
   • synonyms: stand in, sub, substitute
4. write all the required information onto a form
   • "fill out this questionnaire, please!"; "make out a form"
   • synonyms: complete, fill out, make out