What's the Word? is a brain puzzle game developed by Red-Spell for the iOS and Android. It is the original "4 pictures one word" game and has spawned many imitators, notably 4 Pics 1 Word by LOTUM GmbH and 4 Pics 1 Word: What's the Word by Itch Mania.
The four picture one word games exploded in popularity in February 2013 and much of this success has been attributed to this original game.