noun
plural -tions
[count] an explanation of the meaning of a word, phrase, etc. :a statement that defines a word, phrase, etc.
a statement that describes what something is
[singular] :a clear or perfect example of a person or thing
[noncount] :the quality that makes it possible to see the shape, outline, and details of something clearly
by definition
because of what something or someone is :according to the definition of a word that is being used to describe someone or something