diagonal.
http://wiki.answers.com/Q/What_is_a_line_segment_c...

Diagonal (adjective) in
http://www.chacha.com/question/whatisalinesegm...

A line segment connecting two nonadjacent
http://www.chacha.com/question/whatdoyoucalla...

A line segment connecting two nonadjacent vertices of a polygon is called a diagonal. Use the link below to verify this and gather more information.
http://wiki.answers.com/Q/What+is+a+line+segment+c...
