A fleck is a small patch that is different and stands out from the background, like the flecks of green in your blue eyes. A fleck can also be a fragment of something, like the flecks of peeling paint you might see on the floor in an old building.
The noun fleck can describe a color or a spot of light that stands out, like a fleck of orange in a brown and white plaid, or the little bits of light reflected off a sequined top. It can also describe a particle, such as a fleck of dirt you track into your house on your shoe. Fleck can also be a verb that means dotting or marking something with little spots, like when you fleck paint on the wall to produce a random dotted effect.