The Collaborative International Dictionary of English v.0.48:

Y \Y\ (w[imac]), n.; pl. Y's (w[imac]z) or Ys.
   Something shaped like the letter Y; a forked piece resembling
   in form the letter Y. Specifically:
   (a) One of the forked holders for supporting the telescope of
       a leveling instrument, or the axis of a theodolite; a
       wye.
   (b) A forked or bifurcated pipe fitting.
   (c) (Railroads) A portion of track consisting of two
       diverging tracks connected by a cross track.
       [1913 Webster]

   Y level (Surv.), an instrument for measuring differences of
      level by means of a telescope resting in Y's.

   Y moth (Zool.), a handsome European noctuid moth Plusia
      gamma) which has a bright, silvery mark, shaped like the
      letter Y, on each of the fore wings. Its larva, which is
      green with five dorsal white species, feeds on the
      cabbage, turnip, bean, etc. Called also gamma moth, and
      silver Y.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Y \Y\ (w[imac]).
   Y, the twenty-fifth letter of the English alphabet, at the
   beginning of a word or syllable, except when a prefix (see
   Y-), is usually a fricative vocal consonant; as a prefix, and
   usually in the middle or at the end of a syllable, it is a
   vowel. See Guide to Pronunciation, [sect][sect] 145, 178-9,
   272.
   [1913 Webster]

   Note: It derives its form from the Latin Y, which is from the
         Greek [Upsilon], originally the same letter as V.
         Etymologically, it is most nearly related to u, i, o,
         and j. g; as in full, fill, AS. fyllan; E. crypt,
         grotto; young, juvenile; day, AS. d[ae]g. See U, I,
         and J, G.
         [1913 Webster]

   Note: Y has been called the Pythagorean letter, because the
         Greek letter [Upsilon] was taken to represent the
         sacred triad, formed by the duad proceeding from the
         monad; and also because it represents the dividing of
         the paths of vice and virtue in the development of
         human life.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Y \Y\ ([imac]), pron.
   I. [Obs.] --King Horn. --Wyclif.
   [1913 Webster] Y

The Collaborative International Dictionary of English v.0.48:

Y- \Y-\, or I- \I-\ . [OE. y-, i-, AS. ge-, akin to D. & G. ge-,
   OHG. gi-, ga-, Goth. ga-, and perhaps to Latin con-;
   originally meaning, together. Cf. Com-, Aware, Enough,
   Handiwork, Ywis.]
   A prefix of obscure meaning, originally used with verbs,
   adverbs, adjectives, nouns, and pronouns. In the Middle
   English period, it was little employed except with verbs,
   being chiefly used with past participles, though occasionally
   with the infinitive. Ycleped, or yclept, is perhaps the only
   word not entirely obsolete which shows this use.
   [1913 Webster]

         That no wight mighte it see neither yheere. --Chaucer.
   [1913 Webster]

         Neither to ben yburied nor ybrent.       --Chaucer.
   [1913 Webster]

   Note: Some examples of Chaucer's use of this prefix are; ibe,
         ibeen, icaught, ycome, ydo, idoon, ygo, iproved,
         ywrought. It inough, enough, it is combined with an
         adjective. Other examples are in the Vocabulary.
         [1913 Webster] Spenser and later writers frequently
         employed this prefix when affecting an archaic style,
         and sometimes used it incorrectly.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Y
    n 1: a silvery metallic element that is common in rare-earth
         minerals; used in magnesium and aluminum alloys [syn:
         yttrium, Y, atomic number 39]
    2: the 25th letter of the Roman alphabet [syn: Y, y, wye]

The Free On-line Dictionary of Computing (30 December 2018):

Y

   1. General purpose language syntactically like RATFOR,
   semantically like C.  Lacks structures and pointers.  Used
   as a source language for Jack W. Davidson and Christopher
   W. Fraser's peephole optimiser which inspired GCC RTL and
   other optimisation ideas.

   (ftp://ftp.cs.princeton.edu/pub/y+po.tar.Z).  It is a copy
   of the original distribution from the University of Arizona
   during the early 80's, totally unsupported.

   ["The Y Programming Language", D.R. Hanson, SIGPLAN Notices
   16(2):59-68 (Feb 1981)].

   [Jack W. Davidson and Christopher W. Fraser, "The Design and
   Application of a Retargetable Peephole Optimiser", TOPLAS,
   Apr.  1980].

   [Jack W. Davidson, "Simplifying Code Through Peephole
   Optimisation" Technical Report TR81-19, The University of
   Arizona, Tucson, AZ, 1981].

   [Jack W. Davidson and Christopher W. Fraser, "Register
   Allocation and Exhaustive Peephole Optimisation"
   Software-Practice and Experience, Sep. 1984].

   2. See fixed point combinator.


U.S. Gazetteer Places (2000):

Y-O Ranch, WY -- U.S. Census Designated Place in Wyoming
   Population (2000):    242
   Housing Units (2000): 86
   Land area (2000):     2.436005 sq. miles (6.309225 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.436005 sq. miles (6.309225 sq. km)
   FIPS code:            86737
   Located within:       Wyoming (WY), FIPS 56
   Location:             42.035835 N, 104.939874 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Y-O Ranch, WY
    Y-O Ranch
    Y, WY
    Y


U.S. Gazetteer Places (2000):

Y, AK -- U.S. Census Designated Place in Alaska
   Population (2000):    956
   Housing Units (2000): 818
   Land area (2000):     333.415653 sq. miles (863.542540 sq. km)
   Water area (2000):    3.107994 sq. miles (8.049668 sq. km)
   Total area (2000):    336.523647 sq. miles (871.592208 sq. km)
   FIPS code:            86470
   Located within:       Alaska (AK), FIPS 02
   Location:             62.036803 N, 149.987154 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Y, AK
    Y