From the second edition (1989):
(ˈærɪstɑːk) [ad. L. Aristarchus, a. Gr. Ἀρίσταρχος, name of a severe Greek critic of the Homeric poetry, who rejected many lines of it as spurious; hence used connotatively.]

A severe critic. Ariˈstarchian a., severely critical.

1621 Molle Camerar. Liv. Lib. Pref., Learned and judicious Aristarchs. 1751 J. Brown Shaftesb. Charact. 364 Who‥hath chastised the noble writer somewhat roughly, and Aristarchus-like. 1820 Scott Abbot Introd. (1831) 5 Even the aristarch Johnson allowed that, etc. 1853 F. Hall in Leslie's Misc. II. 169 Grave aristarchs vouchsafed to accept it as matter of creed, rather than of criticism.