The term FILLS IN can refer to several different activities. TEMPS is a 5-letter word meaning 'temporary workers, ' who are hired to fill in for a short period of time. ENTER is a 6-letter word meaning 'to ENTER data into a computer system.' SUBS is a 4-letter word meaning 'SUBSTITUTES, ' who are hired to fill in for someone else on a more permanent basis. CLUES is a 5-letter word meaning 'hints or suggestions, ' which can be used to help someone fill in a crossword puzzle.