The Collaborative International Dictionary of English v.0.48:

Entity \En"ti*ty\, n.; pl. Entities. [LL. entitas, fr. L. ens,
   entis, thing, prop. p. pr. of esse to be: cf. F. entit['e].
   See Essence, Is.]
   A real being, whether in thought (as an ideal conception) or
   in fact; being; essence; existence.
   [1913 Webster]

         Self-subsisting entities, such as our own personality.
                                                  --Shairp.
   [1913 Webster]

         Fortune is no real entity, . . . but a mere relative
         signification.                           --Bentley.
   [1913 Webster]

WordNet (r) 3.0 (2006):

entity
    n 1: that which is perceived or known or inferred to have its
         own distinct existence (living or nonliving)

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "entity":
   an existence, article, being, body, creature, critter, ens,
   entelechy, esse, essence, existence, existent, individual, integer,
   integral, integrate, item, life, material, materiality, matter,
   module, monad, object, occurrence, organism, person, persona,
   personality, point, presence, quantity, quiddity, quintessence,
   single, singleton, something, soul, stuff, subsistence, substance,
   substantiality, sum, system, thing, totality, unit



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

entity

    In an entity-relationship model, an entity is a
   type of thing being modeled such as "person" or "product".
   Different entities have different sets of attributes such as
   "name" or "price" and are connected via relationships like
   "bought".  Entities are closely related to classes (class).

   (2009-11-22)