These math dictionaries are for grades Kg.-6.

http://www.hbschool.com/glossary/math2/index_temp.html

Math Dictionary /Grades up to 8th

http://www.harcourtschool.com/glossary/math_advantage/glossary8.html

http://www.coolmath.com/reference/online-math-dictionary.html

Math Terms Through High School

http://www.mathwords.com/a.htm

Mathematical Symbols

http://searchdatacenter.techtarget.com/definition/Mathematical-Symbols