An area seen as a dark spot on the PHOTOSPHERE of the sun. Sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups. They appear dark because they are cooler than the surrounding photosphere. Larger and darker sunspots sometimes are surrounded (completely or partially) by penumbrae. The dark centers are umbrae. The smallest, immature spots are sometimes called pores.
ON-LINE GLOSSARY OF SOLAR-TERRESTRIAL TERMS of National Geophysics Data Center

A region on the surface (photosphere) of the sun that is temporarily cool and dark compared to surrounding areas. See Sunspots and the Solar Max and ACRIMSAT fact sheet.
NASA Earth Observatory

Sunspots - A dark area, which is strongly magnetic, that occurs in the area of the photosphere on the disk of the sun.
[Science; v262; 1372-3; 1993.]
[Science; v266; 1072-3; 1994.]
Atmospheric Chemistry Glossary