1.affectedly grand or important; pompous
2.more complicated or elaborate than necessary; overblown
3.grand in an imposing or impressive way.
4.Having an exaggerated belief in one's importance, sometimes reaching delusional proportions, and occurring as a common symptom of mental illnesses, as manic disorder.

fucking awesome; sexy

The ever evolving collection of cultural beliefs describing the racial identity of African Americans that is both immune from introspection by its own race, can not be observed correctly from outside of the race due to a perceived lack of life experience. At the same time it is omni-intelligent and can observe other races without direct experience and with a perceived lack of bias that no one will challenge.

An ever growing list of positive attributes that can only be obtained by blackness, and an ever growing list of negative qualities that are permanently attached to any amount of whiteness without cause.

An ever growing list of challenges that black people face caused directly by every individual white person.

The observer refuses to observe the observer, and any outsider who makes a contrarian observation is racist.

A debate between a man and his own shadow.

What does it actually mean?

conceited
adjective
excessively proud of oneself; vain.
"Fred's so conceited he'd never believe anyone would refuse him"

grandiose
adjective
impressive and imposing in appearance or style, especially pretentiously so.
"the court's grandiose facade"

sense
noun
a way in which an expression or a situation can be interpreted; a meaning.
"it is not clear which sense of the word ‘characters’ is intended in this passage"

Stringing all these definitions, you get
A person who is excessively proud of oneself, with a way in which an expression or a situation can be interpreted, which is impressive and imposing in appearance or style, (especially pretentiously so)

To call someone a Grandiose or a Grandiose N****r has nothing to do with the character being grandiose, nor is it a play on their ethnicity. It is simply an expression of exasparation at a friend's behaviour.
synonims include: Ass, the N word, Giggan***a