Noah Webster's New International Dictionary of the English Language

1. (a.) In the form of, or bounded by, a circle; round.

2. (a.) repeating itself; ending in itself; reverting to the point of beginning; hence, illogical; inconclusive; as, circular reasoning.

3. (a.) Adhering to a fixed circle of legends; cyclic; hence, mean; inferior. See Cyclic.

4. (a.) Addressed to a circle, or to a number of persons having a common interest; circulated, or intended for circulation; as, a circular letter.

5. (a.) Perfect; complete.

6. (n.) A circular letter, or paper, usually printed, copies of which are addressed or given to various persons; as, a business circular.

7. (n.) A sleeveless cloak, cut in circular form.