[a. Gr. ὖ ψιλόν ‘slender u,’ the adj. having reference to its later sound (ü).]
1. The Greek letter Υ, υ (originally V, Y) representing the vowel u (see U, V, and Y). Also attrib., = having the form of this letter.
1642. Howell, For. Trav., xi. (Arb.), 56. In some places of the Morea … they confound these three letters η, ι, υ (Eta, Iota, Upsilon).
1693. Dryden, Persius, Sat., iii. 109, note. Pithagoras of Samos made the allusion of the Y, or Greek Upsilon, to Vice and Virtue.
1763. Ann. Reg., Misc., 194/1. The last notes … (pronounced as the Greek upsilon, or the French u).
1799. Townson, Tracts & Observ. Nat. Hist., 75. The upsilon Cartilage.
1820. T. S. Hughes, Trav. Sicily, I. 245. The only people who pronounce the letter upsilon like the Italian u.
1854. Bushnan in Orr’s Circ. Sci., Org. Nat., I. 121. The hyoid bone is described as having the shape of the Greek upsilon.
2. Ent. A species of moth (see quot.).
1832. Rennie, Brit. Butterfl. & M., 59. The Upsilon (Orthosia Upsilon, Ochsenheimer) appears in July,… the stigmata pale, between which is a black mark resembling a Y or V.
Hence Upsilonism, tendency to use the letter u.
1879. T. F. Simmons, Lay Folks Mass Bk., Introd. p. lvi. The perpetual upsilonism of our West-Midland text E.
