The Collaborative International Dictionary of English v.0.48:

Peer \Peer\, n. [OE. per, OF. per, F. pair, fr. L. par equal.
   Cf. Apparel, Pair, Par, n., Umpire.]
   1. One of the same rank, quality, endowments, character,
      etc.; an equal; a match; a mate.
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            In song he never had his peer.        --Dryden.
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            Shall they consort only with their peers? --I.
                                                  Taylor.
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   2. A comrade; a companion; a fellow; an associate.
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            He all his peers in beauty did surpass. --Spenser.
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   3. A nobleman; a member of one of the five degrees of the
      British nobility, namely, duke, marquis, earl, viscount,
      baron; as, a peer of the realm.
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            A noble peer of mickle trust and power. --Milton.
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   House of Peers, The Peers, the British House of Lords.
      See Parliament.

   Spiritual peers, the bishops and archibishops, or lords
      spiritual, who sit in the House of Lords.
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The Collaborative International Dictionary of English v.0.48:

Peer \Peer\ (p[=e]r), v. i. [imp. & p. p. Peered; p. pr. & vb.
   n. Peering.] [OF. parir, pareir equiv. to F. para[^i]tre to
   appear, L. parere. Cf. Appear.]
   1. To come in sight; to appear. [Poetic]
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            So honor peereth in the meanest habit. --Shak.
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            See how his gorget peers above his gown! --B.
                                                  Jonson.
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   2. [Perh. a different word; cf. OE. piren, LG. piren. Cf.
      Pry to peep.] To look narrowly or curiously or intently;
      to peep; as, the peering day. --Milton.
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            Peering in maps for ports, and piers, and roads.
                                                  --Shak.
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            As if through a dungeon grate he peered.
                                                  --Coleridge.
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The Collaborative International Dictionary of English v.0.48:

Peer \Peer\ v. t.
   To make equal in rank. [R.] --Heylin.
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The Collaborative International Dictionary of English v.0.48:

Peer \Peer\ v. t.
   To be, or to assume to be, equal. [R.]
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WordNet (r) 3.0 (2006):

peer
    n 1: a person who is of equal standing with another in a group
         [syn: peer, equal, match, compeer]
    2: a nobleman (duke or marquis or earl or viscount or baron) who
       is a member of the British peerage
    v 1: look searchingly; "We peered into the back of the shop to
         see whether a salesman was around"

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "peer":
   Brahman, appear, archduke, aristocrat, armiger, associate, autopsy,
   baron, baroness, baronet, be curious, become visible,
   bend the eyes, blue blood, bore, break through,
   burn with curiosity, canvass, check, check out, check over,
   check up on, coequal, colleague, compeer, confrere, count,
   counterpart, countess, daimio, delve into, dig around for,
   dig into, dig up, direct the eyes, ditto, duchess, duke, earl,
   emerge, equal, equipollent, equivalent, esquire, examine, explore,
   eye, fathom, fellow, gape, gaup, gawk, gentleman,
   give an examination, glare, gloat, go into, go over, goggle,
   grand duke, grandee, hidalgo, indagate, inquire, inspect,
   interrogate, investigate, lace-curtain, lady, laird, landgrave,
   like, look, look at, look into, look over, lord, lordling, magnate,
   magnifico, marchioness, margrave, marquis, match, mate, monitor,
   noble, nobleman, noblewoman, nose around for, nose out, observe,
   opposite number, optimate, overhaul, overlook, palsgrave, parallel,
   pass over, pass under review, patrician, peek, peep, peep out,
   peer at, peer into, peruse, play peekaboo, plumb, poke into,
   pore over, postmortem, probe, pry, pry into, query, question, quiz,
   review, rival, rubber, rubberneck, run over, scan, scrutinize,
   search into, seek, seigneur, seignior, set an examination, show,
   sift, silk-stocking, size, size up, snoop, sound, sovereign, spy,
   squire, stare, study, survey, swell, take a peep, take stock of,
   take the measure, thoroughbred, twin, upper-cruster, viscount,
   viscountess, waldgrave, want to know



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

peer

    A unit of communications hardware or software
   that is on the same protocol layer of a network as another.
   A common way of viewing a communications link is as two
   protocol stacks, which are actually connected only at the
   very lowest (physical) layer, but can be regarded as being
   connected at each higher layer by virtue of the services
   provided by the lower layers.  Peer-to-peer communication
   refers to these real or virtual connections between
   corresponding systems in each layer.

   To give a simple example, when two people talk to each other,
   the lowest layer is the physical layer which concerns the
   sound pressure waves travelling from mouth to ear (so mouths
   and ears are peers) the next layer might be the speech and
   hearing centres in the people's brains and the top layer their
   cerebellums or minds.  Although, barring telepathy, nothing
   passes directly between the two minds, there is a peer-to-peer
   communication between them.

   (2007-03-27)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

PEER. Equal. A man's peers are his equals. A man is to be tried by his
peers.
     2. In England and some other countries, this is a title of nobility;
as, peers of the realm. In the United States, this equality is not so much
political as civil. A man who is not a citizen, is nevertheless to be tried
by citizens.