A grainy photograph looks rough, as if the picture were made of tiny spots instead of a smooth surface. Old film did this when the light was poor or the film was “fast”; digital photos do it when the camera is pushed in the dark (people still say grain even when they mean digital noise). You might hear a grainy shot, grainy footage, a grainy print. The feeling is a little old, a little dirty, sometimes chosen on purpose for mood. Though actually, grainy is also used for other rough textures — grainy mustard, a grainy voice — but this sense is the picture one: the image looks speckled.