fillin

Fill-in is a term with several related senses centered on completion or substitution. As a noun or verb, it denotes something that fills a gap, someone who temporarily substitutes for another, or the act of supplying missing information. The usual spelling is hyphenated when used as a compound noun or adjective, such as fill-in form or fill-in staff.

In employment, a fill-in is a temporary worker who covers duties during an absence, a vacancy, or a project peak. Fill-ins are common in education, healthcare, and service industries, and may be provided by staffing agencies, temporary agencies, or internal staff hired to cover short periods.

In data entry and publishing, a fill-in field is a space in a form or template where information must be entered. Electronic forms often call these fillable fields, and the act of entering data is to fill in the form.

In puzzles and games, a fill-in puzzle requires placing words or phrases into a grid or slots, guided by clues or word lists. Fill-in crosswords, for example, present a set of words to be fit into the grid, with no predefined starting positions.

Etymology: from the phrasal verb "fill in." In modern usage, the hyphenated form is standard, and the term appears across business, publishing, technology, and entertainment contexts.