πιστικός, πιστικη, πιστικον (πιστός), pertaining to belief;

a. having the power of persuading, skillful in producing belief: Plato, Gorgias, p. 455 a. b. trusty, faithful, that can be relied on: γυνή πιστικη καί οἰκουρός καί πειθομενη τῷ ἀνδρί, Artemidorus Daldianus, oneir. 2, 32; often so in Cedrenus (also (of persons) in Epiphanius, John Moschus, Sophronius of Damascus; cf. Sophocles’ Lexicon, under the word); of commodities equivalent to δόκιμος, genuine, pure, unadulterated: so νάρδος πιστικη (but A. V. spike-(i. e. spiked) nard, after thenardispicati of the Vulg. (in Mark)), Mar 14:3; Joh 12:3 (for nard was often adulterated; see Pliny, h. n. 12,26; Dioscorides (?) de mater. med. 1, 6 and 7); hence, metaphorically, τό πιστικον τῆς καινῆς διαθήκης κρᾶμα, Eusebius, dem. evang. 9, 8 (p. 439 d.). Cf. the full discussion of this word in Fritzsche on Mark, p. 596ff; Lücke on Joh 12:3, p. 494ff; Winer’s Grammar, 97f (92f); (especially Dr. James Morison on Mark, the passage cited).