† usationObs.—1 [ad.med.L. *ūsātiōn-, ūsātio, noun of action f.ūsāre to use. Cf.Sp.usacion.] Customary action; established usage. 1556J. Heywood Spider & Fly xxxvii. 25 If..the flies do here pike That quarell to spiders, in customes vsacion. That is tit for tat.