freckle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of the small brownish spots on the skin that turn darker or increase in number upon exposure to the sun.
• transitive & intransitive verb To dot or become dotted with freckles or spots of color.

from The Century Dictionary.

• To mark with freckles or spots: as, his face was freckled by the sun.
• To become covered with freckles: as, the face freckles by exposure.
• noun A brownish-yellow spot in the skin, particularly on the face, neck, or hands, either hereditary or produced by exposure to the sun. These spots usually occur in large number, and are due to increase in the pigment of the lower layers of the epidermis.
• noun Any small spot or discoloration; a fleck.

from the GNU version of the Collaborative International Dictionary of English.

• noun A small yellowish or brownish spot in the skin, particularly on the face, neck, or hands.
• noun Any small spot or discoloration.
• intransitive verb To become covered or marked with freckles; to be spotted.
• transitive verb To sprinkle or mark with freckles or small discolored spots; to spot.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A small brownish or reddish pigmentation spot on the surface of the skin.
• verb transitive To cover with freckles.
• verb intransitive To become covered with freckles.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb become freckled
• noun a small brownish spot (of the pigment melanin) on the skin
• verb mark with freckles