Rhombus
Looks like a diamond
Flat surface with four equal straight sides
but the angles are not always right angles.
Good Links
http://dictionary.kids.net.au/word/rhombus
http://www.mathsisfun.com/definitions/rhombus.html
http://www.mathsisfun.com/geometry/rhombus.html
http://www.coolmath.com/reference/rhombus.html
http://www.k6-geometric-shapes.com/rhombus-shape.html
http://learningideasgradesk-8.blogspot.com/2011/09/geometry-what-is-rhombus.html
http://www.kidspot.com.au/kids-activities-and-games/Learning-games+2/Shapes-for-kids-Rhombus+12512.htm
Video
http://www.youtube.com/watch?v=mZOkpmh_ARw
http://www.youtube.com/watch?v=UnoKXI2_51c&feature=related
http://www.youtube.com/watch?v=v1amjbnYrjY