What is a word for someone who intentionally ignores other people a lot?
If somebody is ignoring others out of superiority complex, then the word is snobbish.
If somebody is ignoring others out of one's reserved nature, then the word can be aloof.
The word I would use is rude.
Consider self-absorbed (“Overly concerned about oneself, to the point of ignoring the feelings of others”); inconsiderate (“Not considerate of others, thoughtless”); egotistical (“Believing oneself to be better and more important than others”), and arrogant (“Having excessive pride in oneself, often with contempt for others”).