ACCIDENTAL definition: happening by chance or accident; not planned; unexpected. See examples of accidental used in a sentence. Anything accidental happens by chance or unintentionally. People don't mean to do accidental things. Accidental is an adjective that refers to something occurring unexpectedly, unintentionally, or by chance, without being planned or foreseen. It can also refer to an incidental or nonessential thing or circumstance. Accidental primarily refers to what occurs by chance: an accidental meeting. It can also mean subordinate or nonessential: Poetry is something to which words are the accidental, not by any means the essential form (Frederick W. Robertson). Accidental describes what was not planned or intended. It means happening by accident or happening as an accident, as in an accidental discovery and an accidental injury. ACCIDENTAL meaning: 1. happening or existing by chance: 2. a sign showing that there is a temporary change from the…. Learn more. Find 53 different ways to say ACCIDENTAL, along with antonyms, related words, and example sentences at Thesaurus.com. ACCIDENTAL definition: 1. happening or existing by chance: 2. a sign showing that there is a temporary change from the…. Learn more. An accidental event happens by chance or as the result of an accident, and is not deliberately intended. The jury returned a verdict of accidental death. His hand brushed against hers; it could have been either accidental or deliberate. Some common synonyms of accidental are casual, contingent, and fortuitous. While all these words mean not amenable to planning or prediction, accidental stresses chance.