To extend under, or be opposed to; as, the line of a triangle which subtends the right angle; the chord subtends an arc.
The angle that an object appears to take up in your field of view; actually, the angle between lines drawn from opposite sides of the object to your eye. For example, the full moon subtends 1/2°.
be opposite to; of angles and sides, in geometry
To extend under; found at the base of.
to extend under or to be opposite of