Cir·cu·lar a.
 1. In the form of, or bounded by, a circle; round.
 2. repeating itself; ending in itself; reverting to the point of beginning; hence, illogical; inconclusive; as, circular reasoning.
 3. Adhering to a fixed circle of legends; cyclic; hence, mean; inferior. See Cyclic poets, under Cyclic.
    Had Virgil been a circular poet, and closely adhered to history, how could the Romans have had Dido?   --Dennis.
 4. Addressed to a circle, or to a number of persons having a common interest; circulated, or intended for circulation; as, a circular letter.
    A proclamation of Henry III., . . . doubtless circular throughout England.   --Hallam.
 5. Perfect; complete. [Obs.]
 A man so absolute and circular
 In all those wished-for rarities that may take
 A virgin captive.   --Massinger.
 Circular are, any portion of the circumference of a circle.
 Circular cubics Math., curves of the third order which are imagined to pass through the two circular points at infinity.
 Circular functions. Math. See under Function.
 Circular instruments, mathematical instruments employed for measuring angles, in which the graduation extends round the whole circumference of a circle, or 360°.
 Circular lines, straight lines pertaining to the circle, as sines, tangents, secants, etc.
 Circular noteor Circular letter. (a) Com. See under Credit. (b) Diplomacy A letter addressed in identical terms to a number of persons.
 Circular numbers Arith., those whose powers terminate in the same digits as the roots themselves; as 5 and 6, whose squares are 25 and 36. --Bailey. --Barlow.
 Circular points at infinity Geom., two imaginary points at infinite distance through which every circle in the plane is, in the theory of curves, imagined to pass.
 Circular polarization. Min. See under Polarization.
 Circular sailing or Globular sailing Naut., the method of sailing by the arc of a great circle.
 Circular saw. See under Saw.