As its other name implies, this is the sort of definition one is likely to find in the dictionary.
Note that a lexical definition is descriptive, reporting actual usage within speakers of a language, and changes with changing usage of the term, rather than prescriptive, which would be to stick with a version regarded as "correct", regardless of drift in accepted meaning.
They tend to be inclusive, attempting to capture everything the term is used to refer to, and as such are often too vague for many purposes.
Lexical words are those that have independent meaning (such as a Noun (N), verb (V), adjective (A), adverb (Adv), or preposition (P)).
Meanings of words given in a dictionary are lexical definitions.