Criss-cross puzzle
A criss-cross puzzle is a crossword-shaped grid supplied with no clues at all — instead you are given the complete list of words, and the puzzle is working out which word belongs in which slot.
The word list is normally grouped by length, and length is also the way in. If exactly one word has nine letters and exactly one slot is nine squares long, that word is placed with certainty before you have thought about anything else. Each placed word fixes letters in the slots that cross it, and those fixed letters eliminate candidates elsewhere, so the grid unravels from its rarest lengths inwards.
Because no clue is ever read, the puzzle needs no vocabulary, no trivia and no shared cultural reference. It is a constraint problem wearing a crossword's clothes, which makes it a favourite for classrooms, language learners and anyone who finds clue-writing wit more irritating than fun.
The same puzzle is sold under several names depending on where you buy it: word fit, fill-in, kriss kross, and criss-cross.
Criss-Cross Puzzle Maker — build one from your own word list and print it with an answer key.