You've played Charades, where one player acts out a word (or phrase or the title of a book or movie) and all the others to try to guess the word or phase from that player's mime. It's a party game stalwart that's been played for more than 300 years; you'll even find it referred to in Charlotte Bronte's Jane Eyre and William Thackeray's Vanity Fair. Plenty of modern party games have incorporated elements of Charades; for example, Time's Up (R & R Games) and Cranium (Funko Games). Reverse Charades (Eagle-Gryphon/The Op) has been a popular variant, switching things around so multiple players are acting and just one player is trying to make sense of the multitude of mimes. Act Fast Speed Charades is similar to Reverse Charades except that the 'actors' have only 15 seconds to convey each word... Oh, and in this game they are all acting different words to each other.
The Act Fast package from Cheatwell Games and Outset Media contains 140 cards, each with three simple words that are intended to be easy to convey, and nine 15-second sand timers. The game is designed to be played with 2-4 actors and one guesser, but you can double or treble this player count by dividing players into teams. The actors have to flip a timer when they start a mime and the guesser has to guess their word before the timer runs out. When you're playing any game with sand timers it's always a chore to keep track of the timer while concentrating on the task at hand (in this case acting or guessing) so it's a notable strength of Pam Walls' design that a player is designated each round with the sole task of policing the timers - calling time when a timer runs out and keeping score.
Act Fast makes for a frenetically fast game. Charades in its original parlour-game form can be quite a genteel pastime but Act Fast Speed Charades is decidedly more chaotic, if sometimes frustrating for the high-octane actors competing with each other for attention. If you want to reduce stress levels, you'd best find some 30- or 45-second timers to substitute for the unforgiving 15-second timers in the box :-)