A speckle is a dot or dash of something — you might think you've painted the living room without spilling any paint, only to find a speckle of purple in the middle of the rug.
Young children pouring their own cereal often leave a speckle of milk on the counter no matter how careful they are. You can also use speckle as a verb meaning "to scatter" or "to dot." For example, you could describe the black spots that speckle your cat, or talk about the stars that speckle the sky. Speckle most likely comes from the Old English word specca, "small spot or speck."