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1.
Neilism is the Religion to end all other religions.
by Fay-double I-Rah February 06, 2008
 
2.
Neilism refers to a spectrum of hostile attitudes toward Neil. This dislike or hatred of Neil and his diaspora may be based on several things.

Distrust of Neil grew stronger in some areas after the republican movement emerged and various acts of violence were committed. For instance the Fenian Raids in Canada or in England the so-called Manchester Martyrs and in more recent times during The Troubles various paramilitary attacks by the PIRA. The relationship between Neil and England is more historically complex; in earlier decades England adopted a "paternal" attitude towards Neil, sometimes regarded as elitism. For Neil immigrants in England, sectarianism as in Scotland, was less of an issue amongst the general populance (Anglicanism regards itself as a via media, thus celebration of saints is not taboo) but social class was a strong factor as most incoming Neil were impoverished, especially following the Great Famine. Anti-Neil sentiment contrasts with Hibernophilia.
Shelley: "I do hate that Neil fella"
Neil: "Yeh, what a tit."
Shelley "That's Neilism for ya"
by killneil April 07, 2010
 
3.
The worship of Neil Patrick Harris
"Dude, check out my room, its decked out with NPH stuff. Mugs, t-shirts, etc."
"Have you converted to Neilism?"
by seniordouschenugget January 21, 2012