stopped down???

I have been reading forums and other materials about photography . I have found the term "stopped down" many times but I don't know what it means. Can some one explained to me?

Could be one of two things but basically they're related anyway. It's unlikely, but maybe it's in reference to an older camera and lens that don't have an automatic aperture. These lenses would be opened up to maximum aperture so you could see easier thru the viewfinder to compose and focus, then "stop down" to the meter reading (f8, for example) to take the shot. Large format cameras operate this way too.

Usually it is just a slang expression for using a smaller aperture. For example, some people say that lenses are usually sharpest "stopped down" one or two stops from wide open. What this means is that if you have an f2.8 lens, it's sharpest at f4 or f5.6 (don't take this as an absolute, just an example, BTW). Another example is that maybe you want a lot of depth of field so you "stop down" to f11 or something.