Definition of "constructible"

Of a land, suitable or allowable for constructing a building on.  examples

Of a building or other thing, capable of being constructed.  examples

(of a regular polygon) That can be constructed in a plane using only a pair of compasses and a straightedge.  examples

(of a complex number) Such that the line segment joining it to the origin can be constructed using only a pair of compasses and a straightedge.  examples