I've seen references in more than one place to 'cook' a grenade, i.e. shorten it's fuse length. But I haven't seen any references in game to doing so, or more importantly, how to do so. How do you cook a grenade in game?
It's rather easy; hold down the throw button (default right-mouse on PC) before throwing it. Dishonored provides you a neat little UI indicator telling you how long you have until it blows. Hold it as long as you need, then throw. Do make sure to leave enough time for the grenade to get where it's going.