1.VerbTo use an angle to delimit (mark off, enclose) part of a straight or curved line, for example an arc or the opposite side of a triangle.
"A 43° angle subtends an arc of about 0.75 meters on a circle with a radius of 1 meter."
2.VerbTo extend or stretch opposite something; to be part of a straight or curved line that is opposite to and delimits an angle.
"A hypotenuse subtends the right angle of a right triangle.; An arc measuring about 0.75 meters on a circle with a radius of 1 meter subtends an angle of about 43°."
3.VerbTo form the central angle of a circle underneath an arc.
"The points A and B on the circumference form the arc AB, which subtends the central angle θ."
4.VerbTo stand beneath or close to, as a bract at the base of a flower.