What is the meaning of Holy Spirit in Mark 3:28-29? Mark 3:28-29
28 : Truly I tell you, people can be forgiven all their sins and every
slander they utter,
29 : but whoever blasphemes against the Holy Spirit
will never be forgiven; they are guilty of an eternal sin.

As here mentioned, what does the Holy spirit is referred to as:

is that refers to the Holy Spirit or the man who get Holy Spirit (general)?

If that refers to the Holy Spirit, how we can sin against Holy Spirit or blaspheme them?
The Holy Spirit is the Holy Ghost, the third member of the Godhead (Father, Son, Holy Ghost)

Book of Mormon, Alma 39:6 gives us further insight on this scripture:


  6  For behold, if ye deny the Holy Ghost when it once has had place in you, and ye know that ye deny it, behold, this is a sin which is unpardonable; yea, and whosoever murdereth against the light and knowledge of God, it is not easy for him to obtain forgiveness; yea, I say unto you, my son, that it is not easy for him to obtain a forgiveness.


What does it mean to deny the Holy Ghost?

Moroni 8:28


  28 Pray for them, my son, that repentance may come unto them. But behold, I fear lest the Spirit hath ceased striving with them; and in this part of the land they are also seeking to put down all power and authority which cometh from God; and they are denying the Holy Ghost.