This is the 12405th most frequent Polish word.
mówiącym
"Speaking" or "talking."
Here, "mówiącym" is an adjective describing the person who is performing the action of speaking English.
Rozmawiamy o człowieku mówiącym płynnie po angielsku.
We are talking about a person speaking English fluently.
In this case, "mówiącym" acts as a participle referring to people who speak the language.
Mówiącym w tym języku jest zawsze łatwiej zrozumieć kulturę.
For those speaking this language, it is always easier to understand the culture.
Here, "mówiącym" identifies the student who is characterized by the act of speaking.