Definition of "yod"

In the Rite of Perfection as worked in France and America this Cabalistic influence is shown in those degrees known under the name of the "Ineffable Degrees," derived from the Jewish belief in the mystery that surrounds the Ineflable Name of God. According to the custom of the Jews, the sacred name Jehovah or Jah-ve, composed of the four letters yod, he, vau, he, which formed the Tetragrammaton, was never to be pronounced by the profane, who were obliged to substitute for it the word "Adonai."

1856, Nesta H. Webster, Secret Societies And Subversive Movements‎

It is really a corruption of, or perhaps rather a substitution for, the Hebrew letter (yod), which is the initial of the ineffable name.

1882, Albert G. Mackey, The Symbolism of Freemasonry‎

A statement of consonantal changes for Sicilian is dependent on the development of two sets of clusters, consonant plus yod and consonant plus /l/.

1976, Michael L. Mazzola, Proto-Romance and Sicilian, Peter de Ridder Press, page 104

Wherever in the West (including northern Italia) the fricative allophone [x̺] of coda /k/ before onsets /t/ and /s/ still remains…it now becomes semivocalized as yod, or more probably voiceless yod….

1984, Frederick B. Agard, A Course in Romance Linguistics, volume 2, Georgetown University Press, page 75

Word-initial yod, however, does not strengthen in either of the dialects considered, which respond to Polish jabłko, jagoda, jelén, jutro (all [j-]) "apple, berry, deer, tomorrow" with unaltered initial yod.

2008, Philippe Ségéral, Tobias Scheer, “Positional Factors in Lenition and Fortition”, in Joaquim Brandão de Carvalho et al., editors, Lenition and Fortition, Mouton de Gruyter, page 152

An' every blessed minute I stannin' there, can't I hear that ole Miz Blatch nex' do', out in her back yod an' her front yod, an' plum out in the street, hollerin': 'Kitty?

1922, Booth Tarkington, Gentle Julia‎