The term ONE-WORD DEFS refers to a type of crossword puzzle in which each clue is answered with a single WORD. This type of puzzle is often used to test the knowledge of language and vocabulary of the solver. The term SYNS (4 letters) is an abbreviation for synonyms, which are words that have the same or similar meanings. Therefore, in this type of crossword puzzle, the solver must find the synonym of the given clue.