Definition of "orbicular"

[…] the Method used by Sailors when they mutiny, by signing their names in an orbicular manner, which they call a round Robin; […]

1731 The Gentleman's Magazine, Weekly Essays in June 1731, Craftman, Sat. June 5, No. 257, "round+robin" p. 238

The whole covey of victims was thus netted; the household ruin was thus full and orbicular; and in that proportion the tendency of men and women, flutter as they might, would be helplessly and hopelessly to sink into the all-conquering hands of the mighty murderer.

1854, Thomas De Quincey, “On Murder, Considered as One of the Fine Arts. Postscript.”, in Miscellanies (De Quincey’s Works; IV), London: James Hogg & Sons, page 76