S: (n) plane, sheet ((mathematics) an unbounded two-dimensional shape) "we will refer to the plane of the graph as the X-Y plane"; "any line joining two points on a plane lies wholly on that plane"
S: (n) circle (something approximating the shape of a circle) "the chairs were arranged in a circle"
S: (n) square (something approximating the shape of a square)
S: (n) triangle (something approximating the shape of a triangle) "the coastline of Chile and Argentina and Brazil forms two legs of a triangle"
S: (n) column, tower, pillar (anything that approximates the shape of a column or tower) "the test tube held a column of white powder"; "a tower of dust rose above the horizon"; "a thin pillar of smoke betrayed their campsite"
S: (n) plume (anything that resembles a feather in shape or lightness) "a plume of smoke"; "grass with large plumes"