I've run into several recipes which asked for a "splash of" water, soy sauce, etc.  How much is a "splash"?  I assume if it's something more concrete like 1/4 cup, they would have said so.  Since it's a "splash", I just poured some (1/2 a cup) water into a coffee cup and poured once around the pan, although, my control isn't that good so I probably ended up pouring 1/4-1/3 of a cup.  Everything still tasted ok but I'm just curious what a "splash" is. 
I'd have to do some testing to get firmer values for things, but they're still ranges, as it depends on what you're pouring it from.  Here's what I typically use for imprecise measurements:  Liquids   dash : a quick shake from a bottle with a restricted top.  If it doesn't have one of those plastic things in the neck of the bottle, cover the opening partially with your thumb.  (likely less than a teaspoon) splash : From a bottle with an unrestricted top, tip the bottle 'til the liquid starts flowing, then pull it back.  (maybe a couple of tablespoons at most) glug : start pouring at a steep angle, stop when the bottle attempts to aspirate (air is sucked back into the bottle, making a 'glug' sound; very dependent on the size of the bottle opening and liquid's viscocity;  might be a couple of tablespoons to a half cup)   Solid powders/granules   dash : a shake or two from a container w/ a restricted top (eg, a shaker top on spices) pinch : what you can pick up between your thumb and one finger (note: dependent on what you're picking up; you can pick up more flaked salt than fine salt in a pinch) heavy pinch : what you can pick up between your thumb and two fingers   Misc   smidge : very small, but I have no clue.  I typically use a dash or a pinch.  