trin·i·ty (tr?n??-t?)n. pl. trin·i·ties 1. A group consisting of three closely related members. Also called triunity.2. Trinity Theology In most Christian faiths, the union of three divine persons, the Father, Son, and Holy Spirit, in one God. Also called Trine.3. Trinity Trinity Sunday.[Middle English trinite, from Old French, from Latin tr?nit?s, from tr?nus, trine; see trine.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.trinity (?tr?n?t?) n, pl -ties1. a group of three2. the state of being threefold[C13: from Old French trinite, from Late Latin tr?nit?s, from Latin tr?nus triple]Trinity (?tr?n?t?) n1. (Theology) Christian theol Also called: Holy Trinity or Blessed Trinity the union of three persons, the Father, Son, and Holy Spirit, in one Godhead2. (Ecclesiastical Terms) See Trinity Sunday3. (Ecclesiastical Terms) Holy Trinity a religious order founded in 1198Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Trin?i?ty (?tr?n ? ti) n., pl. -ties for 2,4. 1. the union of three persons (Father, Son, and Holy Ghost) in one Godhead, or the threefold personality of the one Divine Being. 2. Trinity Sunday. 3. (l.c.) a group of three; triad. 4. (l.c.) the state of being threefold or triple. [1175?1225; Middle English Trinite