re·li·a·ble (r?-l???-b?l)adj.1. Capable of being relied on; dependable: a reliable assistant; a reliable car.2. Yielding the same or compatible results in different clinical experiments or statistical trials.re·li?a·bil?i·ty, re·li?a·ble·ness n.re·li?a·bly adv.Synonyms: reliable, dependable, responsible, trustworthy, trusty These adjectives mean worthy of reliance or trust: a reliable source of information; a dependable worker; a responsible babysitter; a trustworthy report; a trusty assistant.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.reliabilityThe ability of an item to perform a required function under stated conditions for a specified period of time.Dictionary of Military and Associated Terms. US Department of Defense 2005.Reliability/Unreliability See Also: FIRMNESS, STEADINESS