What is the meaning of Sensu_stricto?

In a narrow sense of a polysemic word that may be used in narrower and broader senses.

In the narrow sense (of a taxon). Added after a taxon to mean the taxon is being used in the sense of the original author, or without taxa which may otherwise be associated with it.

Synonym of stricto sensu

In the narrow sense; narrowly.

sensu stricto (in the narrow sense)

Source: wiktionary.org