The Collaborative International Dictionary of English v.0.48:

Per- \Per-\ [See Per.]
   1. A prefix used to signify through, throughout, by, for, or
      as an intensive as perhaps, by hap or chance; perennial,
      that lasts throughout the year; perforce, through or by
      force; perfoliate, perforate; perspicuous, evident
      throughout or very evident; perplex, literally, to
      entangle very much.
      [1913 Webster]

   2. (Chem.) Originally, denoting that the element to the name
      of which it is prefixed in the respective compounds
      exercised its highest valence; now, only that the element
      has a higher valence than in other similar compounds;
      thus, barium peroxide is the highest oxide of barium;
      while nitrogen and manganese peroxides, so-called, are not
      the highest oxides of those elements.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Per \Per\, prep. [L. Cf. Far, For-, Pardon, and cf. Par,
   prep.]
   Through; by means of; through the agency of; by; for; for
   each; as, per annum; per capita, by heads, or according to
   individuals; per curiam, by the court; per se, by itself, of
   itself. Per is also sometimes used with English words.
   [1913 Webster]

   Per annum, by the year; in each successive year; annually.


   per cent, Per centum, percent, by the hundred; in the
      hundred; a proportion multiplied by one hundred; -- used
      esp. of proportions of ingredients, rate or amount of
      interest, and the like; most commonly used in the
      shortened form per cent; as, 5 is ten per cent of 50. It
      is commonly symbolized with the per cent sign, "%".

   Per diem, by the day. [For other phrases from the Latin,
      see Quotations, Phrases, etc., from Foreign Languages, in
      the Supplement.]
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "per":
   accommodated to, according to, adapted to, adjusted to, after,
   agreeable to, agreeably to, all, answerable to, aside, by,
   by dint of, by means of, by use of, by virtue of, by way of,
   conformable to, congruent with, consistent with, each, for each,
   hereby, herewith, in accordance with, in agreement with,
   in compliance with, in conformity with, in correspondence to,
   in harmony with, in keeping with, in line with, in lock-step with,
   in obedience to, in step with, in uniformity with, in virtue of,
   on, per capita, proper to, suitable for, thanks to, thereby,
   therewith, through, uniform with, upon, vagabond, via, whereby,
   wherewith, wherewithal, with



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

PER
       Packed Encoding Rules (ASN.1)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

PER
       Program Event Recording


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

PER

   1.  Packed Encoding Rules.

   2.  partial equivalence relation.

   (1998-05-27)


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

PER. By. When a writ of entry is sued out against the alienee, or descendant
of the original disseisor, it is then said to be brought in the per, because
the writ states that the tenant had not the entry but by the original wrong
doer. 3 Bl. Com. 181. See Entry, writ of.