dimple

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

• noun A small natural indentation in the flesh on a part of the human body, especially in the cheek or on the chin.
• noun A slight depression or indentation in a surface.
• intransitive verb To form dimples by smiling.
• intransitive verb To produce dimples in.

from The Century Dictionary.

• noun A natural or transient dent or small hollow in some soft part of the surface of the human body, most common in youth, produced especially in the cheek by the act of smiling, and hence regarded in that situation as a sign of joyousness or good humor.
• noun A slight depression or indentation on any surface, as on water when slightly agitated.
• To form dimples; sink into depressions or little inequalities.
• To mark with dimples; produce dimples in: as, a smile dimpled her cheeks.

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

• noun A slight natural depression or indentation on the surface of some part of the body, esp. on the cheek or chin.
• noun A slight indentation on any surface.
• intransitive verb To form dimples; to sink into depressions or little inequalities.
• transitive verb To mark with dimples or dimplelike depressions.

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

• noun A small depression or indentation in a surface.
• noun Specifically, a small natural depression on the skin, especially on the face near the corners of the mouth.
• verb transitive To create a dimple in.
• verb intransitive To create a dimple in one's face by smiling.

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

• noun any slight depression in a surface
• noun a small natural hollow in the cheek or chin
• verb produce dimples while smiling
• verb mark with, or as if with, dimples
• noun a chad that has been punched or dimpled but all four corners are still attached