O.K
Defined in 2 dictionaries — Ballentine's (1916), Black's (1910)
Ballentine's Law Dictionary
James A. Ballentine · 1916
A mark signifying the approval of the maker of it. See 149 Mass. 459, 14 Am. St. Rep. 439, 21 N. E. 765.
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
A conventional symbol, of obscure origin, much used in commercial practice and occasionally in indorsements on legal documents, signifying "correct," "approved," "accepted," "satisfactory," or "assented to." See Getchell & Martin Lumber Co., v. Peterson, 124 Iowa, 599, 100 N. W. 550; Morgan-ton Mfg. Co. v. 6hio River, etc., Ry. Co., 121 N. C. 514, 28 S. E. 474, 61 Am. St. Rep. 679; Citizens' Bank v. Farwell, 56 Fed. 570, 6 C. C. A. 24; Indianapolis, D. & W. R. Co. v. Sands, 133 Ind. 433, 32 N. E. 722.